Semiconductor memory device and manufacturing method thereof

ABSTRACT

A process of forming a 3D memory device includes forming a stacked structure with a plurality of stacked layers, etching the stacked structure to form stepped trenches each comprising a plurality of steps, forming a hard mask layer with a plurality of openings over the stepped trenches, forming a photoresist layer over the hard mask layer, and etching through the plurality of openings using the hard mask layer and the photoresist layers as an etch mask to extend a bottom of the stepped trenches to a lower depth.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. application Ser. No.16/597,603, filed Oct. 9, 2019, which claims priority under 35 U.S.C. §119(a) to Korean patent application number 10-2019-0030157, filed onMar. 15, 2019, which is incorporated by reference herein.

BACKGROUND 1. Technical Field

The present disclosure generally relates to a semiconductor memorydevice and a manufacturing method thereof, and more particularly, to athree-dimensional semiconductor memory device and a manufacturing methodthereof.

2. Related Art

A semiconductor memory device may include a memory cell array includinga plurality of memory cells. In order to improve the degree ofintegration of memory cells, a three-dimensional semiconductor memorydevice has been proposed.

The three-dimensional semiconductor memory device includes memory cellsarranged in three dimensions. In order to improve the degree ofintegration, the number of memory cells vertically stacked on asubstrate may be increased. However, the structural stability of thethree-dimensional semiconductor memory device and the stability of amanufacturing process of the three-dimensional semiconductor memorydevice may be reduced as the number of cell layers increases. Inaddition, some of the process that are used to form single layer devicesor devices with a few layers lead to defects when more layers arepresent.

SUMMARY

In an embodiment of the present disclosure, a method for forming asemiconductor device includes forming a stacked structure having aplurality of stacked layers, forming a plurality of stepped trencheshaving a first depth in the stacked structure by etching the stackedstructure, each of the stepped trenches having first and second opposingstepped sidewalls that each have a plurality of steps, forming an etchstop pattern having a hard mask material over a top surface of thestacked structure, the etch stop pattern including a plurality ofopenings exposing portions of the plurality of stepped trenches, forminga first photoresist pattern over the etch stop pattern, the photoresistpattern filling a first portion of the openings and exposing a secondportion of the openings, and etching the second portion of the openingsusing the etch stop pattern as an etch mask to extend a bottom of thestepped trenches exposed by the second portion of the openings to asecond depth lower than the first depth.

In an embodiment, the semiconductor device has a cell region and acontact region. Etching the second portion of the openings forms a firstgroove, and a first stepped trench of the plurality of stepped trenchesis disposed between the first groove and the cell region. The firstphotoresist pattern is removed from the first portion of the openings,and the process may further include forming a second photoresist patternthat covers the first groove, and etching a third portion of theopenings using the hard mask pattern and the second photoresist patternas etch masks. Etching the third portion of the openings includesforming a second groove adjacent to the first groove, the second groovehaving a depth greater than that of the first groove. Etching the thirdportion of the openings includes forming a third groove adjacent to thesecond groove, the third groove having a depth greater than that of thesecond groove. These steps may form a device with a series of steppedgrooves having different depths.

In an embodiment, the plurality of openings of the etch stop patternextends in a first direction, and the plurality of stepped trenchesextends in a second direction perpendicular to the first direction. Thestacked structure may have a plurality of first layers alternating witha plurality of second layers, the second layers comprising a differentmaterial from the first layers, and each of the steps has at least oneof the first layers and at least one of the second layers.

In an embodiment, the stacked structure comprises at least 32 of thefirst layers and at least 32 of the second layers, and etching thesecond portion of the grooves includes etching at least 8 of thedielectric layers and at least 8 of the conductive material layers. Inanother embodiment, the stacked structure comprises at least 96 of thedielectric layers and 96 of the conductive material layers, and etchingthe second portion of the grooves includes etching at least 16 of thedielectric layers and at least 16 of the conductive material layers.

Edges of openings in the photoresist pattern may be set back from edgesof openings in the etch stop pattern so that edges of the openings inthe etch stop pattern with the hard mask material define sidewalls ofgrooves by a vertical etch process. The first stepped sidewalls may beasymmetric to the second stepped sidewalls, and the second steppedsidewalls may be dummy structures.

In an embodiment, the semiconductor device includes a cell region and acontact region and steps of the first stepped sidewalls are contact padsfor the contact region, and the method includes respectively formingvertical contacts on the contact pads. The openings in the etch maskpattern may be used to form a plurality of grooves having differentdepths, and the method may include filling the plurality of grooves withan insulating material and removing a portion of the insulating materialusing the etch stop pattern as a stop layer.

The openings in the etch stop pattern may be substantially rectangularopenings that are used to define sidewalls of a plurality of groovesthrough a plurality of etching processes, so that the substantiallyrectangular openings define four sidewalls of each of the plurality ofgrooves. The semiconductor device may be a memory device that includesat least 192 layers in the stacked layers.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of embodiments will now be described hereinafter with referenceto the accompanying drawings; however, they may be embodied in differentforms and should not be construed as limited to the embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the examples of embodiments to those skilled in the art.

In the drawings, dimensions may be exaggerated for clarity ofillustration. It will be understood that when an element is referred toas being “between” two elements, it can be the only element between thetwo elements, or one or more intervening elements may also be present.Like reference numerals refer to like elements throughout.

FIGS. 1A and 1B illustrate layouts of a semiconductor memory device inaccordance with an embodiment of the present disclosure.

FIGS. 2A and 2B illustrate cross-sections of the semiconductor memorydevice in accordance with an embodiment of the present disclosure.

FIG. 3 illustrates a stacked structure of each of lower layers and firstand second upper layers, which are shown in FIGS. 2A and 2B.

FIGS. 4A and 4B are sectional views illustrating stepped structuresshown in FIGS. 2A and 2B.

FIGS. 5A and 5B are perspective views illustrating structures of firstto third trenches and grooves, which are shown in FIGS. 1A and 1B.

FIG. 6 is a layout of a lower stack structure in accordance with anembodiment of the present disclosure.

FIGS. 7A and 7B, 8A to 8C, 9A and 9B, 10A and 10B, 11A to 11C, and 12Ato 12C are views illustrating a manufacturing method of thesemiconductor memory device in accordance with an embodiment of thepresent disclosure.

FIGS. 13A and 13B illustrate layouts of a semiconductor memory device inaccordance with an embodiment of the present disclosure.

FIGS. 14A and 14B illustrate cross-sections of the semiconductor memorydevice in accordance with an embodiment of the present disclosure.

FIG. 15 is a sectional view illustrating stepped structures shown inFIGS. 14A and 14B.

FIG. 16 is a perspective view illustrating structures of first andsecond trenches and grooves, which are shown in FIGS. 13A and 13B.

FIGS. 17A and 17B, 18A and 18B, 19A and 19B, 20A and 20B, 21A to 21C,22A and 22B, 23, and 24A and 24B are views illustrating a manufacturingmethod of the semiconductor memory device in accordance with anembodiment of the present disclosure.

FIG. 25 illustrates a layout of a semiconductor memory device inaccordance with an embodiment of the present disclosure.

FIGS. 26A and 26B illustrate cross-sections of the semiconductor memorydevice, which are taken along lines Ab-Ab′ and Bb-Bb′ shown in FIG. 25.

FIGS. 27A and 27B are perspective views illustrating structures of uppergrooves and grooves, which are shown in FIG. 25.

FIGS. 28A and 28B, 29A and 29B, and 30A to 30D are views illustrating amanufacturing method of a semiconductor memory device in accordance withan embodiment of the present disclosure.

FIG. 31 is a block diagram illustrating a configuration of a memorysystem in accordance with an embodiment of the present disclosure.

FIG. 32 is a block diagram illustrating a configuration of a computingsystem in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

The specific structural or functional description disclosed herein ismerely illustrative for the purpose of describing embodiments accordingto the concept of the present disclosure. Embodiments according to thepresent disclosure can be implemented in various forms, and are notlimited to the embodiments set forth herein.

While terms such as “first” and “second” may be used to describe variouscomponents, these terms are used only to distinguish one component fromanother. For example, a first component may be referred to as a secondcomponent, and likewise a second component may be referred to as a firstcomponent.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements mayalso be present. In contrast, when an element is referred to as being“directly connected” or “directly coupled” to another element, nointervening elements are present.

The terms used in the present application are merely used to describeparticular embodiments, and are not intended to limit the presentdisclosure. Singular forms in the present disclosure do not precludemultiple instances of the terms, unless the context clearly indicatesotherwise. It will be further understood that terms such as “including”or “having,” etc., are intended to indicate the existence of thefeatures, numbers, operations, actions, components, parts, orcombinations thereof disclosed in the specification, and are notintended to preclude the possibility that one or more other features,numbers, operations, actions, components, parts, or combinations thereofmay exist or may be added.

The term “substantially” refers to a property, e.g. a shape ororientation, that is within engineering tolerance.

In the drawings, dimensions of components may be exaggerated forconvenience of illustration.

Embodiments provide a stable three dimensional (3D) semiconductor memorydevice and a manufacturing method of the semiconductor memory devicewith reduced costs and defects.

FIGS. 1A and 1B illustrate layouts of a semiconductor memory device inaccordance with an embodiment of the present disclosure. FIG. 1Aillustrates a layout of an upper stack structure UST, and FIG. 1Billustrates a layout of a lower stack structure LST disposed under theupper stack structure UST. FIG. 1A illustrates a layout of an uppermostupper layer 105[n] of the upper stack structure UST, and FIG. 1Billustrates an uppermost lower layer 105[k] of the lower stack structureLST.

Referring to FIGS. 1A and 1B, the semiconductor memory device mayinclude gate stack structures ST1 and ST2. Each of the gate stackstructures ST1 and ST2 may have a cell region R1 and a contact region R2extending in a horizontal direction I from the cell region R1.Directions I, II and III correspond to x, y and z directions in acartesian coordinate system as indicated in the legend, where z is avertical direction and x and y are perpendicular horizontal directions.Each of the gate stack structures ST1 and ST2 may be penetrated bychannel structures CH arranged in the cell region R1. Each of thechannel structures CH may include a semiconductor layer used as achannel region. Although not shown in the drawings, a memory layer maybe formed along an interface between each of the channel structures CHand each of the gate stack structures ST1 and ST2. The memory layer mayinclude a tunnel insulating layer, a data storage layer, and a blockinginsulating layer, which are stacked toward a sidewall of each of thegate stack structures ST1 and ST2 from a sidewall of the channelstructures CH. The tunnel insulating layer may include a silicon oxidelayer through which charges can tunnel. The data storage layer may beformed of a charge trapping layer, a material layer including conductivenano dots, or a phase change material layer. For example, the datastorage layer may be formed of a silicon nitride layer in which chargescan be trapped. The blocking insulating layer may include an oxidecapable of blocking charges.

Each of the gate stack structures ST1 and ST2 may be have an upper stackstructure UST that overlaps with a lower stack structure LST. The upperstack structure UST and the lower stack structure LST are penetrated bya slit 151 extending in the third direction III and the first directionI. The slit 151 is disposed between adjacent gate stack structures ST1and ST2, and separates the gate stack structures ST1 and ST2 from eachother in the second direction II. The contact region R2 of each of thefirst and second gate stack structures ST1 and ST2 may extend in thefirst direction I from the cell region R1. The first gate stackstructure ST1 and the second gate stack structure ST2 may be symmetricalwith respect to the slit 151.

Referring to FIG. 1A, the upper stack structure UST may be divided intoa cell structure CS and first and second dummy structures DS1 and DS2,which are separated from each other by first to third trenches T11 toT13. The first to third trenches T11 to T13 may extend in parallel toeach other in the second direction II, and be spaced apart from eachother in the first direction I. The first to third trenches T11 to T13may overlap with the lower stack structure LST shown in FIG. 1B in thecontact region R2. The slit 151 may divide the first to third trenchesT11 to T13.

The first trench T11 may be disposed between the cell region R1 and thesecond trench T12, and penetrate a portion of the upper stack structureUST. The second trench T12 may penetrate the upper stack structure USTbetween the first trench T11 and the third trench T13. The thirdtrenches T13 may respectively open grooves G11 to G15 shown in FIG. 1B.The third trenches T13 may penetrate the upper stack structure UST. Awidth W11 of the first trench T11 may be less than a width W12 of thesecond trench T12 and a width W13 of each of the third trenches T13.

Each of the gate stack structures ST1 and ST2 may include the upperstack structure UST forming the cell structure CS. The cell structure CSmay be disposed in the cell region R1. An end portion of the cellstructure CS may extend toward the contact region R2 to provide a padregion connected to contact plugs 171 shown in FIG. 2A. The cellstructure CS is penetrated by the channel structure CH in the cellregion R1.

The first and second dummy structures DS1 and DS2 may be spaced apartfrom each other in the horizontal direction by the second and thirdtrenches T12 and T13. The first dummy structure DS1 adjacent to the cellstructure CS may be spaced apart from the cell structure CS in thehorizontal direction by the first trench T11. One second dummy structureadjacent to the first dummy structure DS1 among the second dummystructures DS2 may be spaced apart from the first dummy structure DS1 inthe horizontal direction by the second trench T12. The second dummystructures DS2 may be spaced from each other in the horizontal directionby the third trenches T13. A portion of the upper stack structure USTmay form each of the first and second dummy structures DS1 and DS2.

Referring to FIG. 1B, the lower stack structure LST extends from thecell region R1 to the contact region R2 to surround each of the groovesG11 to G15, and forms the gate stack structures ST1 and ST2. The lowerstack structure LST is penetrated by the channel structures CH in thecell region R1.

The grooves G11 to G15 are disposed in the contact region R2 and spacedapart from each other. The grooves G11 to G15 may extend to differentdepths in the lower stack structure LST. The grooves G11 to G15 may besequentially disposed in the first direction I. However, embodiments ofthe present disclosure are not limited thereto. For example, the groovesG11 to G15 may be arranged in various configurations in the horizontaldirection. The slit 151 may extend through each of the groves G11 toG15. Each of the grooves G11 to G15 may include a first part disposed inthe first gate stack structure ST1 and a second part disposed in thesecond gate stack structure ST2.

The lower stack structure LST may include connection parts disposed inthe contact region R2. For example, the lower stack structure LST mayinclude first connection parts LP1 and a second connection part LP2. Thefirst connection parts LP1 may be parts of the lower stack structureLST, which are disposed between adjacent grooves G11 to G15. The secondconnection part LP2 may be a part of the lower stack structure LST,which extends in the first direction I towards the first connectionparts LP1 from the cell region R1. The second connection part LP2 may beconnected to the first connection parts LP1. Each of the grooves G11 toG15 is surrounded by a sidewall defined by first and second connectionparts.

FIGS. 2A and 2B illustrate cross-sections of the semiconductor memorydevice in accordance with an embodiment of the present disclosure.

FIG. 2A illustrates a cross-section of the semiconductor memory devicetaken along line A-A′ shown in FIG. 1A, and FIG. 2B illustrates across-section of the semiconductor memory device taken along line B-B′shown in FIG. 1A.

Referring to FIGS. 2A and 2B, the lower stack structure LST and theupper stack structure UST may be disposed on a lower structure 101.

The lower structure 101 may include a substrate. The substrate mayinclude at least one of silicon (Si), germanium (Ge), silicon germanium(SiGe), gallium arsenide (GaAs), indium gallium arsenide (InGaAs), oraluminum gallium arsenide (AlGaAs), or any combination thereof. Thesubstrate may be a bulk silicon substrate, a silicon-on-insulatorsubstrate, a germanium substrate, a germanium-on-insulator substrate, asilicon-germanium substrate, or an epitaxial thin film formed through aselective epitaxial growth process.

The lower structure 101 may include a peripheral circuit formed on theabove-described substrate. The peripheral circuit may include a rowdecoder, a page buffer, a column decoder, and the like. At least aportion of the peripheral circuit may overlap with the lower stackstructure LST and the upper stack structure UST.

The lower structure 101 may be covered with an insulating layer 103. Thelower stack structure LST and the upper stack structure UST may bedisposed on the insulating layer 103.

The lower stack structure LST may include lower layers 105[1] to 105[k]stacked on each other. The upper stack structure UST may include firstupper layers 105[k+1] to 105[m] stacked on the lower stack structure LSTand second upper layers 105[m+1] to 105[n] stacked on the first upperlayers 105[k+1] to 105[m].

The grooves G11 to G15 may extend to different depths toward the insideof the lower stack structure LST from a height LV at which an interfacebetween the lower stack structure LST and the upper stack structure USTis disposed. In other words, bottom surfaces of the grooves G11 to G15may be disposed at different levels. The grooves G11 to G15 may beopened by the third trenches T13.

The third trenches T13 may overlap with the grooves G11 to G15. Thethird trenches T13 may extend in the horizontal direction as shown inFIG. 1A to open the uppermost lower layer 105[k] of the lower stackstructure LST. The third trenches T13 extend in the third direction IIIand penetrate the second upper layers 105[m+1] to 105[n] and the firstupper layers 105[k+1] to 105[m]. The third trenches T13 may havesidewalls overlapping with the first connection parts LP1 shown in FIG.1B and sidewalls overlapping with the second connection part LP2 shownin FIG. 1B. The sidewalls of the third trenches T13, which overlap withthe second connection part LP2, are shown in FIG. 2A, and the sidewallsof the third trenches T13, which overlap with the second connection partLP2, are shown in FIG. 2B. A gradient of the sidewall of each of thethird trenches T13, which is shown in FIG. 2A, may be greater than thatof the sidewall of each of the third trenches T13, which is shown inFIG. 2B. For example, a portion of each of the third trenches T13, whichoverlaps with the first connection part LP1 shown in FIG. 2A, may havevertical or substantially vertical sidewalls.

The first trench T11 is disposed between the cell region R1 shown inFIG. 1A and the grooves G11 to G15, and extends in the third directionIII to penetrate the second upper layers 105[m+1] to 105[n]. The firsttrench T11 overlaps with the first upper layers 105[k+1] to 105[m]. Theuppermost first upper layer 105[m] may be a bottom surface of the firsttrench T11.

The second trench T12 extends in the third direction III to penetratethe second upper layers 105[m+1] to 105[n] and the first upper layers105[k+1] to 105[m] between the first trench T11 and the grooves G11 toG15. The second trench T12 may overlap with the lower stack structureLST, and the uppermost lower layer 105[k] may be a bottom surface of thesecond trench T12.

The lower layers 105[1] to 105[k] may constitute the gate stackstructure ST1. Portions of the respective first upper layers 105[k+1] to105[m] constituting the cell structure CS and portions of the respectivesecond upper layers 105[m+1] to 105[n] may constitute the gate stackstructure ST1. The first dummy structure DS1 may overlap with the firstupper layers 105[k+1] to 105[m] of the cell structure CS. The firstdummy structure DS1 may be configured with other portions of therespective second upper layers 105[m+1] to 105[n]. Each of the seconddummy structures DS2 may overlap with the lower stack structure LST.Each of the second dummy structures DS2 may be configured with otherportions of the respective first upper layers 105[k+1] to 105[m] andstill other portions of the respective second upper layers 105[m+1] to105[n]. The flatness in the contact region R2 can be improved by thefirst and second dummy structures DS1 and DS2, which can provide supportto avoid dishing in a polishing operation.

Each of the grooves G11 to G15 and the first to third trenches T11 toT13 may be filled with a gap fill insulating layer 141. Referring to theX, Y and Z regions illustrated in FIG. 2A and FIG. 2B, each of thegrooves G11 to G15 and the first to third trenches T11 to T13 mayinclude a stepped structure comprising a plurality of steps. The steppedstructure formed in each of the first and second trenches T11 and T12and the grooves G11 to G15 may be defined by the layers 105[1] to 105[n]of the gate stack structure ST1, and exposed top surfaces of the stepsmay provide pad regions connected to contact plugs 171. Each of thecontact plugs 171 may extend in the third direction III to penetrate thegap fill insulating layer 141. The X regions and the Y region includeportions of the gate stack structure ST1, which are adjacent to thebottom surfaces of the grooves G11 to G15 and the first and secondtrenches T11 and T12. The Z region includes a portion of the upper stackstructure UST, which overlaps with the second connection part LP2 shownin FIG. 1B and is adjacent to any one of the third trenches T13. Theshape of stepped structures formed in the X regions and the Z region maybe substantially the same.

FIG. 3 illustrates a structure of each of the layers 105 which are shownin FIGS. 2A and 2B.

Referring to FIG. 3, each of the lower layers 105[1] to 105[k], thefirst upper layers 105[k+1] to 105[m], and the second upper layers105[m+1] to 105[n], which are shown in FIGS. 2A and 2B, may comprise aconductive layer 105A and an interlayer insulating layer 105B. Theconductive layer 105A and the interlayer insulating layer 105B may bealternately stacked in the third direction III. Each of the contactplugs 171 shown in FIG. 2A extends to be in contact with a conductivelayer 105A that is exposed in a step.

Referring to FIGS. 2A and 2B, the conductive layers 105A constitutingthe layers 105[1] to 105[n] included in the gate stack structure ST1 mayinclude gate electrodes surrounding the channel structures CH shown inFIGS. 1A and 1B. The gate electrodes may include word lines connected tomemory cells and select lines connected to select transistors. Forexample, the conductive layers 105A included in the second upper layers105[m+1] to 105[n] of the gate stack structure ST1 may be used as firstselect lines, and the conductive layers 105A included in the first upperlayers 105[k+1] to 105[m] and the lower layers 105[1] to 105[k] of thegate stack structure ST1 may be used a word lines or second selectlines.

FIGS. 4A and 4B are sectional views illustrating the stepped structuresshown in FIGS. 2A and 2B. FIG. 4A illustrates a first stepped structureSW1 and a second stepped structure SW2, which are formed in the Xregions shown in FIG. 2A and the Z region shown in FIG. 2B. FIG. 4Billustrates a third stepped structure SW3 formed in the Y region shownin FIG. 2A.

Referring to FIG. 4A, each of the second trench T12, the grooves G11 toG15, and the third trenches T13, which are shown in FIGS. 2A and 2B, mayhave a sidewall of the first stepped structure SW1 and a sidewall of thesecond stepped structure SW2, which face each other. The first steppedstructure SW1 and the second stepped structure SW2 may have differentgradients, or slopes. For example, the first stepped structure SW1 mayhave a gradient smaller than that of the second stepped structure SW2.The first stepped structure SW1 having a relatively small gradient maybe used as a pad region.

Referring to FIG. 4B, the first trench T11 shown in FIGS. 2A and 2B mayinclude sidewalls that have structures symmetrical to each other andface each other. Both of the sidewalls of the first trench T11 may havethe third stepped structure SW3. The third stepped structure SW3 of thefirst trench T11 may be include end portions of the second upper layers105[M+1] to 105[n], which extend toward the sidewalls of the firsttrench T11 shown in FIG. 2A.

Referring back to FIG. 4A, the first stepped structure SW1 may includean upper portion formed in a shape of the third stepped structure SW3shown in FIG. 4B and a lower portion formed in a shape of a fourthstepped structure SW4.

FIGS. 5A and 5B are perspective views illustrating structures of thefirst to third trenches and the grooves, which are shown in FIGS. 1A and1B. FIGS. 5A and 5B illustrate a portion of the gate stack structure.

Referring to FIGS. 5A and 5B, the first to third trenches T11 to T13 aredisposed in the upper stack structure UST, and the grooves G11 to G14are disposed at different depths in the lower stack structure LST.

The first trench T11 has stepped symmetrical sidewalls that face eachother as described with reference to FIG. 4B, and each of both thesidewalls may have a shape of the third stepped structure SW3 shown inFIG. 4B.

The second trench T12 and the third trenches T13 may have the samedepth. Each of the second trench T12 and the third trenches T13 may haveasymmetric sidewalls that face each other and have different gradients.One of the sidewalls of each of the second trench T12 and the thirdtrenches T13 may have the first stepped structure SW1 shown in FIG. 4A,and the other sidewalls of each of the second trench T12 and the thirdtrenches T13 may have the second stepped structure SW2 shown in FIG. 4A.

Each of the grooves G11 to G14 may have a sidewall with the firststepped structure SW1 shown in FIG. 4A and a sidewall with the secondstepped structure SW2 shown in FIG. 4A.

For example, a first groove G11 may include first to third sidewalls S1to S3. The first groove G11 may overlap with first patterns P1 formedwith some of the lower layers constituting the lower stack structureLST. The first groove G11 may be surrounded by second patterns P2, whichare formed with others of the lower layers constituting the lower stackstructure LST and are disposed on the first patterns P1. The firstsidewall S1 of the first groove G11 may be sidewalls of the secondpatterns P2. The second sidewall S2 and the third sidewall S3 of thefirst groove G11 may face each other and extend from the first sidewallS1. The second sidewall S2 may have the first stepped structure SW1shown in FIG. 4A, and the third sidewall S3 may have the second steppedstructure SW2 shown in FIG. 4A.

A second groove G12 may include fourth to sixth sidewalls S4 to S6. Thesecond groove G12 may be surrounded by first patterns P1 and secondpatterns P2. The fourth sidewall S4 of the second groove G12 may becomprise faces of the first patterns P1. The fifth sidewall S5 and thesixth sidewall S6 of the second groove G12 may face each other andextend from the fourth sidewall S4. The fifth sidewall S5 may have thefirst stepped structure SW1 shown in FIG. 4A, and the sixth sidewall S6may have the second stepped structure SW2 shown in FIG. 4A. The secondgroove G12 may further include seventh to ninth sidewalls S7 to S9extending toward the upper stack structure UST respectively from thefourth to sixth sidewalls S4 to S6. The seventh to ninth sidewalls S7 toS9 comprise faces of the second patterns P2.

Each of the first sidewall S1, the fourth sidewall S4, and the seventhsidewall S7 may be formed to have a gradient greater than that of eachof the first stepped structure SW1 and the second stepped structure SW2.For example, the gradient of each of the first sidewall S1, the fourthsidewall S4, and the seventh sidewall S7 may be vertical orsubstantially vertical. The first sidewall S1, the fourth sidewall S4,and the seventh sidewall S7 are sidewalls of the second connection partLP2 shown in FIG. 1B. Since it is unnecessary for the first sidewall S1,the fourth sidewall S4, and the seventh sidewall S7 to provide a padregion, each of the first sidewall S1, the fourth sidewall S4, and theseventh sidewall S7 may not be formed in a stepped structure. In theembodiment of the present disclosure, each of the first sidewall S1, thefourth sidewall S4, and the seventh sidewall S7, have a steep gradient,which occupies less space on a chip leading to greater integration.

FIG. 6 is a layout of a lower stack structure in accordance with anembodiment of the present disclosure. FIG. 6 illustrates a layout withrespect to an uppermost lower layer 205[k] of the lower stack structureLST.

The lower stack structure LST may include the structures described withreference to FIGS. 1B, 2A and 2B, 3, 4A, and 5A and 5B. Hereinafter,redundant descriptions will be omitted.

Each of the lower layers of the lower stack structure LST in accordancewith an embodiment of the present disclosure includes first and secondconnection parts LP1 and LP2 disposed in a contact region R2. The firstand second connection parts LP1 and LP2 may be disposed between a firstcell region R1A and a second cell region R1B of the lower stackstructure LST. A structure formed in each of the first cell region R1Aand the second cell region R1B includes the structure disposed in thecell region R1, which is described with reference to FIG. 1B. Forexample, the first cell region R1A and the second cell region R1B mayhave channel structures CH.

The lower stack structure LST may be gate stack structures. For example,the lower layers of the lower stack structure LST may constitute firstto fourth gate stack structures ST1 to ST4. The first gate stackstructure ST1 and the third stack structure ST3 may share the samecontact region R2, and the second gate stack structure ST2 and thefourth gate stack structure ST4 may share the same contact region R2.

The lower stack structure LST may be penetrated by a slit 251 extendingin the first direction I. The first gate stack structure ST1 and thesecond stack structure ST2 may be spaced apart in the second directionII by the slit 251, and the third gate stack structure ST3 and thefourth gate stack structure ST4 may be spaced apart from each other inthe second direction II by the slit 251.

Grooves G having different depths may be disposed in the contact regionR2 of the lower stack structure LST. The grooves G may be formed in thesame structure as G11 to G15 shown in FIGS. 1B, 2A, 3, 4A, and 5A and5B.

FIGS. 7A and 7B, 8A to 8C, 9A and 9B, 10A and 10B, 11A to 11C, and 12Ato 12C are views illustrating a manufacturing method of thesemiconductor memory device in accordance with an embodiment of thepresent disclosure. The gate stack structures described with referenceto FIGS. 1A and 1B, 2A and 2B, 3, 4A and 4B, and 5A and 5B may be formedusing the embodiments described below.

FIGS. 7A and 7B are plan and sectional views illustrating a process of afirst trench T11 and first preliminary trenches PT1 in a stack structure300. FIG. 7B illustrates a cross-section of the stack structure 300taken along line C-C′ shown in FIG. 7A.

Referring to FIGS. 7A and 7B, the stack structure 300 is formed bystacking a plurality of horizontal layers 305[1] to 305[n] on a lowerstructure 301, which may be the same as the lower structure 101described with reference to FIGS. 2A and 2B. After an insulating layer303 covering the lower structure 301 is formed, the stack structure 300may be formed on the insulating layer 303.

Each of the horizontal layers 305[1] to 305[n] of the stack structure300 may include a cell region R1 and a contact region R2 extending in ahorizontal direction from the cell region R1. The contact region R2 mayextend in a first direction I from the cell region R1. The horizontallayers 305[1] to 305[n] may include lower layers 305[1] to 305[k], firstupper layers 305[k+1] to 305[m], and second upper layers 305[m+1] to305[n].

Each of the horizontal layers 305[1] to 305[n] extends in the firstdirection I and the second direction II. The horizontal layers 305[1] to305[n] may be formed by alternately stacking first material layers andsecond material layers in a third direction III. Each of the horizontallayers 305[1] to 305[n] may be configured with a pair of a firstmaterial layer and a second material layer, which are sequentiallystacked. In an embodiment, each of the first material layers may beformed as the conductive layer 105A described with reference to FIG. 3,and each of the second material layers may be formed as the interlayerinsulating layer 105B described with reference to FIG. 3. In anotherembodiment, the first material layers and the second material layers maybe formed of materials having different etch rates. In an example, eachof the first material layers may be formed as a sacrificial layerreplaced with the conductive layer 105A described with reference to FIG.3 in a subsequent process, and each of the second material layers may beformed as the interlayer insulating layer 105B. In another example, eachof the first material layers may be formed as the conductive layer 105Adescribed with reference to FIG. 3, and each of the second materiallayers may be formed as a sacrificial layer replaced with the interlayerinsulating layer 105B in a subsequent process. Each of the firstsacrificial layers may include a nitride layer, and each of the secondsacrificial layers may include a doped silicon layer.

Subsequently, a first mask pattern 311 may be formed on the stackstructure 300. Before the first mask pattern 311 is formed, processesfor forming the channel structures CH shown in FIGS. 1A and 1B in thecell region R1 of the stack structure 300 may be performed.

The first mask pattern 311 may include a photoresist pattern. The firstmask pattern 311 may include a first opening OP1 and second openingsOP2, which open the contact region R2. The first opening OP1 may bedisposed between the cell region R1 and the second openings OP2. Inother words, the first opening OP1 may be formed closer to the cellregion R1 than the second openings OP2.

The first trench T11 and the first preliminary trenches PT1 may beformed by etching each of the second upper layers 305[m+1] to 305[n],using the first mask pattern 311 as an etch mask. The first trench T11may be formed in a region corresponding to the first opening OP1 of thefirst mask pattern 311, and the first preliminary trenches PT1 may beformed in regions corresponding to the second openings OP2 of the firstmask pattern 311.

Each of the first trench T1 and the first preliminary trenches PT1 mayinclude opposing stepped sidewalls facing each other. the steppedsidewalls may have stepped structures Sa and Sb that are symmetrical toeach other. Each of the stepped structures Sa and Sb may be the thirdstepped structure SW3 described with reference to FIGS. 4A and 4B.

The stepped structures Sa and Sb of each of the first trench T11 and thefirst preliminary trenches PT1 may be formed by repeating an etchingprocess and a slimming process. The etching process is performed byremoving a portion of at least one of the second upper layers 305[m+1]to 305[n], using the first mask pattern 311 as the etch mask. Theetching process may be repeated until each layer of the second upperlayers 305[m+1] to 305[n] is exposed through the first opening OP1 andthe second openings OP2.

Here, the slimming process may include removing material from sidewallsof the first mask pattern 311 such that the width of each of the firstopening OP1 and the second openings OP2 of the first mask pattern 311expands in the horizontal direction. Thus, the process of forming thepreliminary trenches may comprise performing a vertical etch using anisotropic etch process to remove a layer of material 305, performing aslimming process, e.g. an isotropic etching process, to expand the widthof the trenches, and repeating the vertical etch and slimming processesuntil stepped preliminary trenches T11 and PT1 are formed. An uppermostfirst upper layer 305[m] may be exposed by the first trench T11 and thefirst preliminary trenches PT1. In order to save space, a width WA ofthe first trench T11 may be formed narrower than that WB of each of thefirst preliminary trenches PT1.

FIGS. 8A to 8C are views illustrating a process of forming a secondtrench T12 and second preliminary trenches PT2 in the stacked structure300. FIG. 8A is a plan view illustrating a second mask pattern 313. FIG.8B illustrates a cross-section of the stack structure 300 taken alongline C-C′ shown in FIG. 8A. FIG. 8C is an enlarged sectional view ofstepped structures Sa, Sc, and Sd included in each of the second trenchT12 and the second preliminary trenches PT2.

Referring to FIGS. 8A and 8B, the second mask pattern 313 may be formedon the stack structure 300. Before the second mask pattern 313 isformed, the first mask pattern 311 shown in FIGS. 7A and 7B may beremoved. The second mask pattern 313 may include a photoresist pattern.

The second mask pattern 313 may be formed to cover the first trench T11shown in FIG. 8B and to cover one (e.g., Sa) of the stepped structuresSa and Sb of each of the first preliminary trenches PT1 shown in FIGS.7A and 7B. The second mask pattern 313 may include third openings OP3.The third openings OP3 may be formed to have a width narrower than thatof the second openings OP2 shown in FIGS. 7A and 7B. The third openingsOP3 may be biased toward one side of the first preliminary trenches PT1shown in FIGS. 7A and 7B.

The second trench T12 and the second preliminary trenches PT2 may beformed by etching each of the first upper layers 305[k+1] to 305[m],using the second mask pattern 313 as an etch mask. The second upperlayers 305[m+1] to 305[n] defining a stepped structure (e.g., Sb) formedat one sidewall of each of the first preliminary trenches PT1 shown inFIGS. 7A and 7B may be etched through the third openings OP3.

Referring to FIG. 8C, each of the second trench T12 and the secondpreliminary trenches PT2 may include the stepped structure Sa formedthrough the processes described with reference to FIGS. 7A and 7B. Also,each of the second trench T12 and the second preliminary trenches PT2may include the stepped structures Sc and Sd formed through an etchingprocess using the second mask pattern 313 as an etch mask. The steppedstructures Sc and Sd formed through the etching process using the secondmask pattern 313 as an etch mask may be respectively the third steppedstructures SW3 and the fourth stepped structures SW4, which aredescribed with reference to FIG. 4A.

The stepped structures Sc and Sd of each of the second trench T12 andthe second preliminary trenches PT2 may be formed by repeating anetching process and a slimming process.

The etching process is performed to remove a portion of at least one ofthe first upper layers 305[k+1] to 305[m] by using the second maskpattern 313 as an etch mask. The etching process may be repeatedwhenever each of the first upper layers 305[k+1] to 305[m] are exposedthrough the third openings OP3.

The slimming process is a process of removing a portion of the secondmask pattern 313 such that the width of each of the third openings OP3of the second mask pattern 313 expands in the horizontal direction. Theslimming process may be performed before performing a vertical etchingprocess. When the slimming process is repeated, the width of each of thethird openings OP3 may be increased. For example, as shown in FIG. 8C,the width of each of the third openings OP3 may expand in an order of{circle around (1)}, {circle around (2)}, {circle around (3)}, and{circle around (4)}. Whenever the width of each of the third openingsOP3 is increased, the second upper layers 305[m+1] to 305[n] definingthe stepped structure (e.g., Sb) formed at the one sidewall of each ofthe first preliminary trenches PT1 shown in FIGS. 7A and 7B may beexposed and etched.

Each of the second trench T12 and the second preliminary trenches PT2may have the first stepped structure SW1 and the second steppedstructure SW2, which are described with reference to FIG. 4A. Anuppermost lower layer 305[k] may be a bottom surface of the secondtrench T12 and the second preliminary trenches PT2.

FIGS. 9A and 9B are plan and sectional views illustrating a process offorming a first groove G11 and first preliminary grooves PG1. FIG. 9Billustrates a cross-section of the stack structure 300 taken along lineC-C′ shown in FIG. 9A.

Referring to FIGS. 9A and 9B, a third mask pattern 315 may be formed onthe stack structure 300. Before the third mask pattern 315 is formed,the second mask pattern 313 shown in FIGS. 8A and 8B may be removed. Thethird mask pattern 315 may include a photoresist pattern.

The third mask pattern 315 may be formed to cover the first trench T11and the second trench T12. The third mask pattern 315 may be formed tocover some of the second preliminary trenches PT2 shown in FIGS. 8A and8B, and include openings OP4 exposing remaining second preliminarytrenches PT2 shown in FIGS. 8A and 8B. The fourth openings OP4 may beformed to be spaced apart from each other.

Some layers disposed under the uppermost lower layer 305[k] are etchedusing the third mask pattern 315 as an etch mask. The first and secondupper layers 305[k+1] to 305[n] exposed by the fourth openings OP4 maybe etched.

The first stepped structure SW1 and the second stepped structure SW2,which are exposed through each of the fourth openings OP4 by theabove-described etching process, are moved to a first depth d1, which isdeeper than the depth of each of the first trench T11 and the secondtrench T12 in the stack structure 300. In other words, a vertical etchis performed on openings OP4 that increases a depth of alternatingtrenches.

The first groove G11 and the first preliminary grooves PG1 are extendedto the first depth d1 in the stack structure 300 by the above-describedetching process. The first groove G11 is disposed in a regioncorresponding to one of the fourth openings OP4, and the firstpreliminary grooves PG1 are disposed in regions corresponding toremaining fourth openings OP4.

FIGS. 10A and 10B are plan and sectional views illustrating a process offorming a second groove G12, a third groove G13, a second preliminarygroove PG2, and a third preliminary groove PG3. FIG. 10B illustrates across-section of the stack structure 300 taken along line C-C′ shown inFIG. 10A.

Referring to FIGS. 10A and 10B, a fourth mask pattern 317 may be formedon the stack structure 300. Before the fourth mask pattern 317 isformed, the third mask pattern 315 shown in FIGS. 9A and 9B may beremoved. The fourth mask pattern 317 may include a photoresist pattern.

The fourth mask pattern 317 may be formed to cover the first trench T11,the second trench T12, and the first groove G11. The fourth mask pattern317 may include fifth openings OP5 and sixth openings OP6. The fifthopenings OP5 respectively expose the second preliminary trenches PT2shown in FIGS. 9A and 9B. The sixth openings OP6 respectively expose thefirst preliminary grooves PG1 shown in FIGS. 9A and 9B. The fifthopenings OP5 are formed in an alternating arrangement with the sixthopenings OP6.

At least some of the lower layers 305[1] to 305[k] are etched using thefourth mask pattern 317 as an etch mask. The first and second upperlayers 305[k+1] to 305[n] exposed by the fifth and sixth openings OP5and OP6 may be etched as well. In particular, a vertical etch process,e.g. an isotropic etching, may be performed to extend the depth of thetrenches downwards by several layers while preserving the stepped shapeof the trenches.

The first stepped structure SW1 and the second stepped structure SW2,which are exposed through each of the fifth openings OP5 by theabove-described etching process, are moved to a second depth d2 deeperthan the first depth dl in the stack structure 300. In addition, thefirst stepped structure SW1 and the second stepped structure SW2, whichare exposed through the sixth openings OP6 by the above-describedetching process, are moved to a third depth d3 deeper than the seconddepth d2 in the stack structure 300.

The second groove G12 and the second preliminary groove PG2 are disposedat the second depth d2 in the stack structure 300 by the above-describedetching process, and the third groove G13 and the third preliminarygroove PG3 are disposed at the third depth d3 in the stack structure 300by the above-described etching process.

FIGS. 11A to 11C are views illustrating a process of forming a fourthgroove G14 and a fifth groove G15. FIG. 11A is a plan view illustratinga fifth mask pattern 319. FIG. 11B illustrates a cross-section of thestack structure 300 taken along line C-C′ shown in FIG. 11A. FIG. 11Cillustrates a cross-section of the stack structure 300 taken along lineD-D′ shown in FIG. 11A.

Referring to FIGS. 11A to 11C, the fifth mask pattern 319 may be formedon the stack structure 300. Before the fifth mask pattern 319 is formed,the fourth mask pattern 317 shown in FIGS. 10A and 10B may be removed.The fifth mask pattern 319 may include a photoresist pattern.

The fifth mask pattern 319 may be formed to cover the first trench T11,the second trench T12, and the first to third grooves G11 to G13. Thefifth mask pattern 319 may include a seventh opening OP7 and an eighthopening OP8. The seventh opening OP7 exposes the second preliminarygroove PG2 shown in FIGS. 10A and 10B, and the eighth opening OP8exposes the third preliminary groove PG3 shown in FIGS. 10A and 10B. Theseventh opening OP7 and the eighth opening OP8 are spaced apart fromeach other.

At least some of the lower layers 305[1] to 305[k] are etched using thefifth mask pattern 319 as an etch mask. The first and second upperlayers 305[k+1] to 305[n] exposed by the seventh and eighth openings OP7and OP8 may be etched as well. In particular, a vertical etch process,e.g. an isotropic etching, may be performed to extend the depth of thetrenches downwards by several layers while preserving the stepped shapeof the trenches.

The first stepped structure SW1 and the second stepped structure SW2,which are exposed through the seventh opening OP7 by the described-aboveetching process, are moved to a fourth depth d4 deeper than the thirddepth d3 in the stack structure 300. In addition, the first steppedstructure SW1 and the second stepped structure, which are exposedthrough the eighth opening OP8 by the above-described etching process,are moved to a fifth depth d5 deeper than the fourth depth d4 in thestack structure 300.

The fourth groove G14 is disposed at the fourth depth d4 in the stackstructure 300 by the above-described etching process, and the fifthgroove G15 is disposed at the fifth depth d5 in the stack structure 300by the above-described etching process.

Dotted lines shown in FIG. 11A represent a layout of the first to thirdgrooves G11 to G13.

Referring to FIG. 11A, each of the first to fifth grooves G11 to G15 aresurrounded by the lower layers 305[1] to 305[k] shown in FIG. 11B. Thelower layers 305[1] to 305[k] shown in FIG. 11B may surround each of thefirst to fifth grooves G11 to G15, to define first to fourth sidewalls1W to 4W of each of the first to fifth grooves G11 to G15. The firstsidewall 1W and the second sidewall 2W may face each other in the firstdirection I, and the third sidewall 3W and the fourth sidewall 4W mayface each other in the second direction II.

The first stepped structure SW1 and the second stepped structure SW2,which are described with reference to FIG. 4A, may be formed adjacent toa bottom surface of each of the first to fifth grooves G11 to G15disposed at different depths. For example, a lower portion of the firstsidewall 1W of each of the first to fifth grooves G11 to G15 may have afirst stepped structure SW1 corresponding thereto, and a lower portionof the second sidewall 2W of each of the first to fifth grooves G11 toG15 may have a second stepped structure SW2 corresponding thereto.

FIGS. 12A to 12C are views illustrating a process of forming a slit 335.FIG. 12A is a plan view illustrating a sixth mask pattern 331. A dottedline shown in FIG. 12A represents a layout of the first to fifth groovesG11 to G15. FIG. 12B illustrates a cross-section of the stack structure300 taken along line C-C′ shown in FIG. 12A. FIG. 12C illustrates across-section of the stack structure 300 taken along line D-D′ shown inFIG. 12A.

Referring to FIGS. 12A to 12C, the sixth mask pattern 331 may be formedon the stack structure 300. Before the sixth mask pattern 331 is formed,the first trench T11, the second trench T12, and the first to fifthgrooves G11 to G15 may be filled with a gap fill insulating layer 321.In accordance with an embodiment of the present disclosure, the first tofifth grooves G11 to G15 are locally formed in the contact region R2 ofthe stack structure 300. The flatness of a surface of the stackstructure 300 can be improved by portions of the stack structure 300,which remain around the first to fifth grooves G11 to G15. The portionsof the stack structure 300 which remain around the first to fifthgrooves G11 to G15 may be the first and second dummy structures DS1 andDS2 described with reference to FIGS. 2A and 2B. When the flatness ofthe stack structure 300 is improved, a step difference in the gap fillinsulating layer 321 is minimized, and thus the flatness of a surface ofthe gap fill insulating layer 321 can be improved.

Before the sixth mask pattern 331 is formed, a planarization process forplanarizing the surface of the gap fill insulating layer 321, such asChemical Mechanical Polishing (CMP), may be further performed. Also,before the sixth mask pattern 331 is formed, the fifth mask pattern 319shown in FIGS. 11A to 11C may be removed.

The sixth mask pattern 331 may extend to the contact region R2 from thecell region R1. The sixth mask pattern 331 may include a ninth openingOP9 exposing the stack structure 300. The ninth opening OP9 may extendto the contact region R2 from the cell region R1. The ninth opening OP9may be disposed between the third sidewall 3W and the fourth sidewall4W.

A portion of each of the horizontal layers 305[1] to 305[n] of the stackstructure 300 are etched using the sixth mask pattern 331 as an etchmask. Accordingly, the slit 335 penetrating the stack structure 300 isformed. The stack structure 300 may be separated into a plurality ofstack patterns by the slit 335. For example, the stack patterns mayinclude a first stack pattern STa and a second stack pattern STb, whichare separated by the slit 335.

In an embodiment, the first and second stack patterns STa and STb may berespectively used as the first and second gate stack structures ST1 andST2 described with reference to FIGS. 1A and 1B. In another embodiment,in order to form the first and second gate stack structures ST1 and ST2described with reference to FIGS. 1A and 1B, sacrificial layers of eachof the horizontal layers 305[1] to 305[n] constituting the second andsecond stack patterns STa and STb may be replaced with a conductivelayer or an interlayer insulating layer.

Subsequently, a process of filling the slit 335 with a verticalstructure and a process of forming the contact plugs 171 shown in FIG.2A may be performed.

FIGS. 13A and 13B illustrate layouts of a semiconductor memory device inaccordance with an embodiment of the present disclosure. FIG. 13Aillustrates a layout of an upper stack structure UST, and FIG. 13Billustrates a layout of a lower stack structure LST′ disposed under theupper stack structure UST′. FIG. 13A illustrates a layout of anuppermost upper layer 405[n] of the upper stack structure UST, and FIG.13B illustrates an uppermost lower layer 405[k] of the lower stackstructure LST′. The embodiment of FIGS. 13A and 13B is similar to theembodiment of FIGS. 1A and 1B, so descriptions of some elements that areredundant to the descriptions for FIGS. 1A and 1B are omitted.

Referring to FIGS. 13A and 13B, the semiconductor memory device mayinclude gate stack structures ST11 and ST12. Each of the gate stackstructures ST11 and ST12 may have a cell region R1 and a contact regionR2 extending in a horizontal direction from the cell region R1.

Each of the gate stack structures ST11 and ST12 may be penetrated bychannel structures CH disposed in the cell region R1. Although not shownin FIGS. 13A and 13B, a sidewall of each of the channel structures CHmay be surrounded by a memory layer. The channel structures CH and thememory layer may be formed with the same material layers as describedwith reference to FIGS. 1A and 1B.

Each of the gate stack structures ST11 and ST12 may have an upper stackstructure UST′ that overlaps with a lower stack structure LST′. Theupper stack structure UST′ and the lower stack structure LST′ arepenetrated by a slit 451.

Referring to FIG. 13A, the upper stack structure UST′ may be dividedinto a cell structure CS and dummy structures DS, which are separatedfrom each other by a first trench T21 and second trenches T22, which aredisposed in the contact region R2.

The first trench T21 may be disposed between the cell region R1 and thesecond trenches T22. The second trenches T22 may respectively open thegrooves G21 to G25 shown in FIG. 13B. The first trench T21 and thesecond trenches T22 may penetrate the upper stack structure UST′.

Each of the gate stack structures ST11 and ST12 may include the upperstack structure UST′ forming the cell structure CS. The cell structureCS may be disposed in the cell region R1. An end portion of the cellstructure CS may extend toward the contact region R2 to provide a padregion connected to contact plugs 471 shown in FIG. 14A. The cellstructure CS is penetrated by the channel structure CH in the cellregion R1.

The dummy structures DS may be spaced apart from each other in thehorizontal direction by the second trenches T22. The cell structure CSmay be spaced apart from the dummy structures DS in the horizontaldirection by the first trench T21.

Referring to FIG. 13B, the lower stack structure LST′ extends to thecontact region R2 from the cell region R1, surrounds each of the groovesG21 to G25, and constitute each of the gate stack structures ST11 andST12. The lower stack structure LST′ is penetrated by the channelstructures CH in the cell region R1.

The grooves G21 to G25 are disposed in the contact region R2 to bespaced apart from each other. The grooves G21 to G25 may extend todifferent depths in the lower stack structure LST′. The grooves G21 toG25 may be arranged in a line in first direction I. However, embodimentsof the present disclosure are not limited thereto. For example, thegrooves G21 to G25 may be arranged in various structures in thehorizontal direction. The slit 451 may extend through each of the grovesG21 to G25. Each of the grooves G21 to G25 may include a part surroundedby the first gate stack structure ST11 and a part surrounded by thesecond gate stack structure ST12.

The lower stack structure LST′ may include a connection parts disposedin the contact region R2. For example, the lower stack structure LST′may include first connection parts LP1′ and a second connection partLP2′. The first connection parts LP1′ may be disposed between adjacentgrooves G21 to G25. The second connection part LP2′ may extend to beconnected to the first connection parts LP1′ from the cell region R1.

FIGS. 14A and 14B illustrate cross-sections of the semiconductor memorydevice in accordance with an embodiment of the present disclosure. FIG.14A illustrates a cross-section of the semiconductor memory device takenalong line Aa-Aa′ shown in FIG. 13A, and FIG. 14B illustrates across-section of the semiconductor memory device taken along line Ba-Ba′shown in FIG. 13A.

Referring to FIGS. 14A and 14B, the lower stack structure LST′ and theupper stack structure UST′ may be disposed on a lower structure 401.

The lower structure 401 may be the same as the lower structure 101described with reference to FIG. 2A. The lower structure 401 may becovered with an insulating layer 403. The insulating layer 403 mayinclude insulating material having a multi-layer.

The lower stack structure LST′ may include lower layers 405 [1] to405[k] stacked on each other. The upper stack structure UST′ may includeupper layers 405[k+1] to 405[n] stacked on the lower stack structureLST′.

The grooves G21 to G21 may extend to different depths toward the insideof the lower stack structure LST′ from a height LV′ at which aninterface between the lower stack structure LST′ and the upper stackstructure UST′ is disposed. The grooves G21 to G25 may be opened by thesecond trenches T22.

The first trench T21 and the second trenches T22 extend in a thirddirection III and penetrate the upper layers 405[k+1] to 405[n].

The first trench T21 is disposed between the cell region R1 and thegrooves G21 to G25, which are shown in FIG. 13A. The first trench T21overlaps with the lower layers 405 [1] to 405[k]. The uppermost lowerlayer 405[k] may be a bottom surface of the first trench T21.

The second trenches T22 may overlap with the grooves GS21 to G25. Thesecond trenches T22 may extend in the horizontal direction as shown inFIG. 13A, and penetrate the uppermost lower layer 405[k] of the lowerstack structure LST′. The second trenches T22 may have sidewallsoverlapping with the first connection parts LP1′ shown in FIG. 13B andsidewalls overlapping with the second connection part LP2′ shown in FIG.13B. The sidewalls of the second trenches T22, which overlap with thefirst connection parts LP1, are shown in FIG. 14A, and the sidewalls ofthe second trenches T22, which overlap with the second connection partLP2′, are shown in FIG. 14B. The sidewall of each of the second trenchesT22 may have a first portion, which is shown in FIG. 14A, and a secondportion, which is shown in FIG. 14B. A gradient of the first portion maybe greater than that of the second portion. Portions of sidewalls ofeach of the second trenches T22, which are shown in FIG. 14A, may bevertical or substantially vertical.

Each of the cell structure CS and the dummy structures DS may overlapwith the lower stack structure LST′, and be configured with some of theupper layers 405[k+1] to 405[n]. The cell structure CS and the lowerlayers 405[1] to 405[k] may constitute the gate stack structure ST11.The flatness in the contact region R2 can be improved by the dummystructures DS.

Each of the grooves G21 to G25 and the first and second trenches T21 andT22 may be filled with a gap fill insulating layer 441.

Each of the grooves G21 to G25 and the first and second trenches T21 andT22 may include stepped sidewalls facing each other. The steppedstructures formed in the first trench T21 and the grooves G21 to G25 mayprovide pad regions connected to contact plugs 471.

Each of the upper layers 405[k+1] to 405[n] and the lower layers 405[1]to 405[k] may be comprise a conductive layer 105A and an interlayerinsulating layer 105B as described with reference to FIG. 3.

The conductive layers included in the upper layers 405[k+1] to 405[n]may be first select lines connected to first select transistors, and theconductive layers included in the lower layers 405[1] to 405[k] may beword lines connected to memory cells or second select lines connected tosecond select transistors.

FIG. 15 is a sectional view illustrating stepped structures shown inFIGS. 14A and 14B. A first stepped structure SW11 and a second steppedstructure SW12, which are shown in FIG. 15, may be formed in each of thegrooves G21 to G25 and the first and second trenches T21 and T22, whichare shown in FIGS. 14A and 14B.

Referring to FIG. 15, the first stepped structure SW11 and the secondstepped structure SW12 may face each other and be symmetrical to eachother.

FIG. 16 is a perspective view illustrating structures of first andsecond trenches T21 and T22 and grooves G21 to G25, which are shown inFIGS. 13A and 13B.

Referring to FIG. 16, the first and second trenches T21 and T22 aredisposed in the upper stack structure UST, and the grooves G21 to G25may be disposed at different depths in the lower stack structure LST′.

Each of the first and second trenches T21 and T22 and the grooves G21 toG25 has a sidewall of the first stepped structure SW11 that faces and issymmetric to a sidewall of the second stepped structure SW12.

The grooves G21 to G25 may be locally formed in the lower stackstructure LST′. For example, a first groove G21 may include first tothird sidewalls S1′ to S3′. The first groove G21 may overlap with firstpatterns P1′ formed with some of the lower layers constituting the lowerstack structure LST′, and be surrounded by second patterns P2′ that aredisposed on the first patterns P1′. The first sidewall S1′ of the firstgroove G21 may be defined along sidewalls of the second patterns P2′.The second sidewall S2′ and the third sidewall S3′ may face each otherand extend from the first sidewall S1′. The second sidewall S2′ may havethe first stepped structure SW11 shown in FIG. 15, and the thirdsidewall S3′ may have the second stepped structure SW12 shown in FIG.15.

A second groove G22 among the grooves G21 to G25 may include fourth tosixth sidewalls S4′ to S6′. The second groove G22 may be surrounded bythe first patterns P1′ and the second patterns P2′. The fourth sidewallS4′ of the second groove G22 may comprise sidewalls of the firstpatterns P1′. The fifth sidewall S5′ and the sixth sidewall S6′ may faceeach other and extend from the fourth sidewall S4′. The fifth sidewallS5′ may have the first stepped structure SW11 shown in FIG. 15, and thesixth sidewall S6′ may have the second stepped structure SW12 shown inFIG. 15. The second groove G22 may further include seventh to ninthsidewalls S7′ to S9′ respectively extending from the fourth to sixthsidewalls S4′ to S6′. The seventh to ninth sidewalls S7′ to S9′ mayextends toward the upper stack structure UST′ from the fourth to sixthsidewall S4′ to S6′.

A gradient of each of the first sidewall S1′, the fourth sidewall S4′,and the seventh sidewall S7′ may be greater than that of a gradient ofeach of the first stepped structure SW11 and the second steppedstructure SW12.

FIGS. 17A and 17B, 18A and 18B, 19A and 19B, 20A and 20B, 21A to 21C,22A and 22B, 23, and 24A and 24B are views illustrating a manufacturingmethod of the semiconductor memory device in accordance with anembodiment of the present disclosure. The gate stack structuresdescribed with reference to FIGS. 13A, 13B, 14A, 14B, 15, and 16 may beformed using the embodiment described below. In addition, the followingprocesses that use a combination of a hard mask layer and a photoresistlayer to vertically etch trenches can be applied to devices withasymmetric trenches as an alternative to the processes described withrespect to FIGS. 9A to 11C.

FIGS. 17A and 17B are plan and sectional views illustrating a process offorming a first trench T21 and preliminary trenches PT in a stackstructure 500. FIG. 17B illustrates a cross-section of the stackstructure 500 taken along line Ca-Ca′ shown in FIG. 17A.

Referring to FIGS. 17A and 17B, the stack structure 500 is formed bystacking a plurality of horizontal layers 505[1] to 505[n] on a lowerstructure 501. The lower structure 501 is the same as the lowerstructure 101 described with reference to FIGS. 2A and 2B. After aninsulating layer 503 covering the lower structure 501 is formed, thestack structure 500 may be formed on the insulating layer 503.

Each of the horizontal layers 505[1] to 505[n] of the stack structure500 may include a cell region R1 and a contact region R2 extending in ahorizontal direction from the cell region R1. The horizontal layers505[1] to 505[n] may include lower layers 505[1] to 505[k] and upperlayers 505[k+1] to 505[n].

Each of the horizontal layers 505[1] to 505[n] may be formed byalternately stacking first material layers and second material layers ina third direction III as described with reference to FIGS. 7A and 7B.

Subsequently, a first mask pattern 511 may be formed on the stackstructure 500. Before the first mask pattern 511 is formed, the channelstructures CH shown in FIGS. 13A and 13B in the cell region R1 of thestack structure 500 may be formed.

The first mask pattern 511 may include a photoresist pattern. The firstmask pattern 511 may include first openings OP11 that open the contactregion R2. The first openings OP11 may extend in parallel to each otherin a first direction, and be spaced apart from each other in a seconddirection perpendicular to the first direction. For example, the firstopenings OP11 may be spaced apart from each other in first direction I,and extend in second direction II.

The first trench T21 and the preliminary trenches PT may be formed byetching each of the upper layers 505[k+1] to 505[n], using the firstmask pattern 511 as an etch mask. The first trench T21 may be a patterndisposed between the cell region R1 and the preliminary trenches PT.

Each of the first trench T21 and the preliminary trenches PT may includesidewalls that face each other and are symmetrical to each other. Boththe sidewalls may have symmetrical stepped structures Se. The steppedstructures SE may be the first stepped structure SW11 and the secondstepped structure SW12, which are described with reference to FIG. 15.However, embodiments are not limited to symmetric stepped structures—inother embodiments, the stepped structures may be asymmetric steppedstructures such as SW1 and SW2 of FIG. 4A.

The stepped structures Se of each of the first trench T21 and thepreliminary trenches PT may be formed by repeating vertical etching andslimming processes as described with reference to FIGS. 7A and 7B.

FIGS. 18A and 18B are plan and sectional views illustrating a process offorming an etch stop pattern 513. FIG. 18B illustrates a cross-sectionof the stack structure 500 taken along line Ca-Ca′ shown in FIG. 18A.

Referring to FIGS. 18A and 18B, the etch stop pattern 513 may be formedon the stack structure 500. Before the etch stop pattern 513 is formed,the first mask pattern 511 shown in FIGS. 17A and 17B may be removed.The etch stop pattern 513 may be formed of a material different fromthose of the stack structure 500 and mask patterns formed in asubsequent process. For example, the etch stop pattern 513 may be a hardmask pattern that includes a polysilicon layer.

In various embodiments, the hard mask pattern may comprise a metalmaterial, a silicide material, a polymeric material, or other hard maskmaterials as known in the art. The etch stop pattern 513 comprising thehard mask material may be formed, for example, by depositing a layer ofhard mask material over an entire surface of the substrate, levellingthe hard mask material, and selectively etching the hard mask materialto form the etch stop pattern 513 shown in FIG. 18A. The etch stoppattern 513 may extend to the contact region R2 from the cell region R1.The etch stop pattern 513 may include second openings OP12 that locallyopen the first trench T21 and the preliminary trenches PT, respectively.The second openings OP12 may be spaced apart from each other.

FIGS. 19A and 19B are plan and sectional views illustrating a process offorming a first groove G21 and first preliminary grooves PG21 using acombination of a hard mask material and a photoresist material. FIG. 19Billustrates a cross-section of the stack structure 500 taken along lineCa-Ca′ shown in FIG. 19A.

Referring to FIG. 19A and 19B, a second mask pattern 515 may be formedon the etch stop pattern 513 to cover the stack structure 500. Thesecond mask pattern 515 may include a photoresist pattern.

The second mask pattern 515 may be formed to cover the cell region R1and the first trench T21. The second mask pattern 515 may be formed tocover a first portion of the preliminary trenches PT, and include thirdopenings OP13 that expose a second portion of the preliminary trenchesPT. Specifically, the openings OP13 may be formed over alternatingtrenches so that every other trench is exposed, as seen in FIG. 19B. Thethird openings OP13 may be spaced apart from each other. When the secondmask pattern 515 is formed over etch stop pattern 513, as shown in FIG.19B, edges of the second mask pattern can be offset from edges of etchstop pattern 513.

While the edges of etch stop pattern will be used to define edges of atrench by an etching operation, the second mask pattern is used toprotect remaining area of the device during the vertical etch process.Therefore, the exact location of edges of the second mask pattern 515for opening OP13 have a relatively high tolerance compared to edges ofthe etch stop pattern 513. When a photoresist pattern is removed andre-applied several times, the looser tolerance reduces the probabilityof an alignment error and simplifies the process.

If the photoresist material is used to define edges of the etchedtrenches, the photoresist must be carefully aligned each time it isdeposited. In contrast, when etch stop pattern 513 is present, a muchlarger tolerance can be used for the photoresist material of second maskpattern 515, which simplifies and reduces the cost of the process. Thelarger tolerance may be manifested by a difference between the edges ofopenings OP13 of the photoresist material and openings OP12 of the hardmask layer, where edges of openings of the photoresist pattern are setback from edges of openings in the etch stop pattern.

Using an etch mask that is a combination of a hard mask material foretch stop pattern 513 and a photoresist pattern 515 for the second maskpattern 515 provides numerous advantages, especially when etchingthrough multiple stack layers 505. When a photoresist layer is used inconjunction with a hard mask layer, the thickness of the photoresistlayer can be substantially reduced. The reduced thickness takes lesstime to form, providing a higher production throughput.

The reduced thickness facilitates curing of the photoresist material,which reduces the amount of time required to cure the material, alsoleading to improved production throughput. Because it is difficult tocure thick photoresist layers, the reduced thickness helps photoprocesses to focus properly and reduces defects from uncured photoresistmaterial. Photoresist layers can build up through multiple etchingprocesses, leading to a significant difference in a cell region comparedto a contact region. While these and other issues can cause the shape ofphotoresist layers to change in an etching process, a hard mask materialis more stable, which improves process reliability and reduces errorrates.

Benefits of using a photoresist material and a hard mask material inconjunction with one another may be more apparent at greater etchdepths. For example, in an embodiment, a stack structure 500 has atleast 64 layers comprising at least 32 layers 105A and 32 layers 105B,and etching a groove includes etching at least 8 layers 105A and 8layers 105B in a single etching process. In another embodiment, a stackstructure 500 has at least 192 layers comprising at least 96 layers 105Aand 96 layers 105B, and etching a groove includes etching at least 16layers 105A and 16 layers 105B in a single etching process.

Each of the third openings OP13 may extend horizontally in parallel tothe preliminary trenches PT. For example, each of the third openingsOP13 may extend in the second direction II. The third openings OP13 maybe spaced apart from each other. A portion of the etch stop pattern 513may be exposed by each of the third openings OP13.

A vertical etch process is performed to etch the preliminary trenchesusing the second mask pattern 515 and the etch stop pattern 513 as anetch mask. In particular, the vertical etching may remove a plurality oflayers 505 to extend the preliminary trenches downwards so that ahighest step of the stepped preliminary trenches is one layer 505 belowthe base layer of trench T21. Accordingly, each layer 505 may have asurface portion that is exposed by at least one of the trenches, and theexposed surface portion is a contact pad which is connected to avertical contact, e.g. a contact 471 in FIG. 14A, in a subsequentprocess. Thus, the stepped structures Se are moved to a first depth d11that is greater than a depth of the first trench T21 by the verticaletching process using a combination of the hard mask material in etchstop pattern 513 and the photoresist material in second mask pattern515.

FIGS. 20A and 20B are plan and sectional views illustrating a process offorming a second groove G22, a third groove G23, a second preliminarygroove PG22, and a third preliminary groove PG23. FIG. 20B illustrates across-section of the stack structure 500 taken along line Ca-Ca′ shownin FIG. 20A.

Referring to FIGS. 20A and 20B, a third mask pattern 517 may be formedon the etch stop pattern 513 to cover the stack structure 500. Beforethe third mask pattern 517 is formed, the second mask pattern 515 shownin FIGS. 19A and 19B may be removed. The third mask pattern 517 mayinclude a photoresist pattern. Because etch stop pattern 513 including ahard mask material remains in place, the tolerances used to form thirdmask pattern 517 can be substantially lower than the tolerances thatwould be required to maintain alignment with edges of the grooves.

The third mask pattern 517 may be formed to cover the cell region R1,the first trench T21, and the first groove G21. The third mask pattern517 may include a fourth opening OP14 that exposes a portion of each ofthe preliminary trenches PT shown in FIGS. 19A and 19B. The fourthopening OP14 may extend in the horizontal direction in parallel to thepreliminary trenches PT. For example, the fourth opening OP14 may extendin the second direction II. A portion of the etch stop pattern 513 maybe exposed by the fourth opening OP14.

At least some of the lower layers 505[1] to 505[k] are etched using thethird mask pattern 517 and the etch stop pattern 513 as an etch mask.The etching process may be performed until the layer 505 below thebottom of groove G21 is exposed as the uppermost step of the steppedsidewall of adjacent groove G22.

Put another way, the stepped structures Se exposed in each of theregions in which the second openings OP12 and the fourth opening OP14overlap with each other are moved to a second depth d12 and a thirddepth d13, which are deeper than the first depth d11.

The second groove G22 and the second preliminary groove PG22 are etchedto the second depth d12 in the stack structure 500 through theabove-described etching process, and the third groove G23 and the thirdpreliminary groove PG23 are etched to the third depth d13 in the stackstructure 500 through the above-described etching process.

FIGS. 21A to 21C are views illustrating a process of forming a fourthgroove G24 and a fifth groove G25. FIG. 21A is a plan view illustratinga fourth mask pattern 519. FIG. 21B illustrates a cross-section of thestack structure 500 taken along line Ca-Ca′ shown in FIG. 21A. FIG. 21Cillustrates a cross-section of the stack structure 500 taken along lineDa-Da′ shown in FIG. 21A.

Referring to FIGS. 21A to 21C, the fourth mask pattern 519 may be formedon the etch stop pattern 513 to cover the stack structure 500. Beforethe fourth mask pattern 519 is formed, the third mask pattern 517 shownin FIGS. 20A and 20B may be removed. The fourth mask pattern 519 mayinclude a photoresist pattern.

The fourth mask pattern 519 may be formed to cover the cell region R1,the first trench T21, and the first to third grooves G21 to G23. Thefourth mask pattern 519 may include a fifth opening OP15. The fifthopening OP15 exposes the second and third preliminary grooves PG22 andPG23 shown in FIGS. 20A and 20B. The fifth opening OP15 may extend inthe horizontal direction parallel to the first trench T21. For example,the fifth opening OP15 may extend in the second direction II. A portionof the etch stop pattern 513 may be exposed by the fifth opening OP15.

At least some of the layers 505 are etched by a vertical etch processusing a combination of the fourth mask pattern 519 and the etch stoppattern 513 as an etch mask. The stepped structures Se exposed in eachof the regions in which the second openings OP12 and the fifth openingOP15 overlap with each other are moved to a fourth depth d14 and a fifthdepth d15, which are deeper than the third depth d13.

The fourth groove G24 is etched to the fourth depth d14 in the stackstructure 500 through the above-described etching process, and the fifthgroove G25 is etched to the fifth depth d15 in the stack structure 500through the above-described etching process. Portions of the upperlayers 505[k+1] to 505[n] of the stack structure 500 which remain aroundthe first to fifth grooves G21 to G25 may be dummy structures DS, whichare described in more detail with reference to FIGS. 14A and 14B.

A plurality of grooves may be formed such that a lowermost lower layer505[1] of the stack structure 500 is exposed using the processesdescribed with reference to FIGS. 17A, 17B, 18A, 18B, 19A, 19B, and 21Ato 21C. In other words, in an embodiment, a series of deposition andetching processes described with respect to these figures are performeduntil the lowermost groove exposes the lower layer 505[1]. In someembodiments, a stack structure may have, for example, 96 layers 505, andeach trench may expose contact pads for 16 of those layers, resulting ina total of 6 trenches. However, numerous other examples are possible.

Using the combination of the hard mask and the photoresist patternprovides a number of advantages compared to a conventional process ofonly using a photoresist layer to create the vertical trenches. As notedabove, when etch stop pattern 513 is present, the tolerances of theopenings OP13, OP14 and OP15 are substantially looser, which greatlysimplifies the deposition processes. When a photoresist layer is usedwithout an etch stop pattern 513, the photoresist layer is relativelythick to fill trenches as well as protect upper surfaces of the device.

It can be challenging to fully cure the photoresist layer when it has asubstantial thickness, which leads to errors in an etching process. Forexample, uncured portions of the mask may be removed by verticaletching, causing uneven sidewalls and mismatch between the mask and thetrenches. In general, thicker layers of photoresist are problematic in aphotocuring operation which has limitations of a depth of focus.However, these issues are substantially reduced by using a combinationof hard mask and photoresist materials as described above.

FIGS. 22A and 22B are plan and sectional views illustrating a process offorming a gap fill insulating layer 521. Dashed lines shown in FIG. 22Arepresent a layout of the first to fifth grooves G21 to G25. FIG. 22Billustrates a cross-section of the stack structure 500 taken along lineCa-Ca′ shown in FIG. 22A.

Referring to FIG. 22A, each of the first to fifth grooves G21 to

G25 is surrounded by the lower layers 505[1] to 505[k] shown in FIG.22B. The lower layers 505[1] to 505[k] shown in FIG. 22B may surroundeach of the first to fifth grooves G21 to G25, to define first to fourthsidewalls 1W′ to 4W′ of each of the first to fifth grooves G21 to G22.The first sidewall 1W′ and the second sidewall 2W′ face each other inthe first direction I, and the third sidewall 3W′ and the fourthsidewall 4W′ face each other in the second direction II. The steppedstructures of each of the first to fifth grooves G21 to G25 may berespectively formed at lower portions of the first sidewall 1W′ and thesecond sidewall 2W′, which are adjacent to a bottom surface of a groove.

Referring to FIGS. 22A and 22B, the gap fill insulating layer 521 isformed on the etch stop pattern 513 to fill a plurality of groovesincluding the first to fifth grooves G21 to G25 and the first trenchT21. In accordance with an embodiment of the present disclosure, theplurality of grooves including the first to fifth grooves G21 to G25 arelocally formed in the contact region R2 of the stack structure 500, sothat the flatness of the gap fill insulating layer 521 can be improved.

FIG. 23 is a sectional view illustrating a first planarization process.

Referring to FIG. 23, the gap fill insulating layer 521 shown in FIGS.22A and 22B may be planarized. The first planarization process may beperformed using Chemical Mechanical Polishing (CMP). The etch stoppattern 513 may be exposed by the planarized gap fill insulating layer521 a. The etch stop pattern 513 may be used as a stop layer in thefirst planarization process. In other embodiments, an etch back processis performed to remove the insulating layer 521, and the etch stoppattern 513 is used as a stop layer for the etch back process. Thus,etch stop pattern 513 may be a stop layer for a removal process that maybe a polishing process or an etch back process.

FIGS. 24A and 24B are views illustrating a process of forming a slit535. Dashed lines shown in FIG. 24A represent a layout of the first tofifth grooves G21 to G25. FIG. 24B illustrates a cross-section of thestack structure 500 taken along line Ca-Ca′ shown in FIG. 24A.

Referring to FIGS. 24A and 24B, a fifth mask pattern 531 may be formedon the stack structure 500. Before the fifth mask pattern 531 is formed,the etch stop pattern 513 shown in FIG. 23 may be removed, and theplanarized gap fill insulating layer 521 a may be planarized through asecond planarization process. The second planarization process may beperformed using an etch-back or CMP process.

The fifth mask pattern 531 may extend to the contact region R2 from thecell region R1. The fifth mask pattern 531 may include a sixth openingOP16 that exposes the stack structure 500. The sixth opening OP16 mayextend to the contact region R2 from the cell region R1. The sixthopening OP16 may not overlap with the plurality of grooves including thefirst to fifth grooves G21 to G25 in the contact region R2.

A portion of each of the horizontal layers 505[1] to 505[n] of the stackstructure 500 is etched using the fifth mask pattern 531 as an etchmask. Accordingly, the slit 535 penetrating the stack structure 500 isformed. The stack structure 500 may be separated into a plurality ofstack patterns by the slit 535. For example, the stack patterns mayinclude a first stack pattern STa′ and a second stack pattern STb′,which are separated by the slit 535.

The first and second stack patterns STa′ and STb′ may be used as thegate stack structures ST11 and ST12 described with reference to FIGS.13A and 13B. In another embodiment, in order to form the gate stackstructures ST11 and ST12 described with reference to FIGS. 13A and 13B,a sacrificial layer of each of the horizontal layers 505[1] to 505[n]constituting the first and second stack patterns STa′ and STb′ may bereplaced with a conductive layer or an interlayer insulating layer.

Subsequently, a process of filling the slit 535 with a verticalstructure and subsequent processes of forming the contact plugs 471shown in FIG. 14A may be performed.

FIG. 25 illustrates a layout of a semiconductor memory device inaccordance with an embodiment of the present disclosure.

Referring to FIG. 25, the semiconductor memory device may include gatestack structures ST21 and ST22. Each of the gate stack structures ST21and ST22 may have a cell region R1 and a contact region R2 extending ina horizontal direction from the cell region R1.

Each of the gate stack structures ST21 and ST22 may be penetrated bychannel structures CH arranged in the cell region R1. Although not shownin FIG. 25, a sidewall of each of the channel structures CH may beadjacent to a memory layer. Materials constituting the each of thechannel structures CH and the memory layer may be the same as describedwith reference to FIGS. 1A and 1B.

The gate stack structures ST21 and ST22 may be separated from each otherby a slit 651. For example, the gate stack structures ST21 and ST22 mayinclude a first gate stack structure ST21 and a second gate stackstructure ST22, which are separated from each other by the slit 651. Thefirst gate stack structure ST21 and the second gate stack structure ST22may be symmetrical to each other with respect to the slit 651.

Each of thin films 605[1] to 605[n] shown in FIGS. 26A and 26B thatconstitute the gate stack structures ST21 and ST22 and are stacked in athird direction III may extend to the contact region R2 from the cellregion R1 to surround each of upper grooves TG1 and TG2 and grooves G31to G35.

The grooves G31 to G35 are disposed in the contact region R2 and spacedapart from each other. The grooves G31 to G35 may have different depths.The grooves G31 to G35 may be arranged in a line in a first direction I.However, the embodiment of the present disclosure is not limitedthereto. For example, the grooves G31 to G35 may be arranged in variousstructures in the horizontal direction. The slit 651 may extend tooverlap with each of the grooves G31 to G35.

The upper grooves TG1 and TG2 may be disposed between the grooves G31 toG35 and the cell region R1. For example, the upper grooves TG1 and TG2may include a first upper groove TG1 disposed between the grooves G31 toG35 and the cell region R1 and a second upper groove TG2 that isdisposed between the first upper groove TG1 and the grooves G31 to G35and is deeper than the first upper groove TG1.

Each of the gate stack structures ST21 and ST22 may include connectionparts disposed in the contact region R2. For example, each of the gatestack structures ST21 and ST22 may include first connection parts LP11and a second connection part LP12. The first connection parts LP11 maybe parts of each of the gate stack structures ST21 and ST22, which arerespectively disposed between the upper grooves TG1 and TG2, betweengrooves G31 to G35, and between the upper groove TG2 and a first grooveG31, which are adjacent to each other. The second connection part LP12may be a portion of each of the gate stack structures ST21 and ST22which connects the first connection parts LP11 from the cell region R1.Each of the upper grooves TG1 and TG2 and the grooves G31 to G35 havesidewalls defined by first and second connection parts LP11 and LP12.

FIGS. 26A and 26B illustrate sections of the semiconductor memory devicewhich are taken along lines Ab-Ab′ and Bb-Bb′ shown in FIG. 25.

Referring to FIGS. 26A and 26B, the gate stack structures ST21 and ST22shown in FIG. 25 may be divided into a lower stack structure LST and anupper stack structure UST. The lower stack structure LST and the upperstack structure UST may be disposed on a lower structure 601 describedwith reference to FIGS. 2A and 2B. The lower structure 601 may becovered with an insulating layer 603.

The lower stack structure LST may include a stack of lower layers 605[1]to 605[k]. The upper stack structure UST may include first upper layers605[k+1] to 605[m] stacked on the lower stack structure LST and secondupper layers 605[m+1] to 605[n] stacked on the first upper layers605[k+1] to 605[m]. Each of the lower layers 605[1] to 605[k], the firstupper layers 605[k+1] to 605[m], and the second upper layers 605[m+1] to605[n] may include a conductive layer 105A and an interlayer insulatinglayer 105B, which are described with reference to FIG. 3.

Each of the grooves G31 to G35 may penetrate the upper stack structureUST and extend to different depths toward the inside of the lowerstructure LST. In other words, bottom surfaces of the grooves G31 to G35may be disposed at different heights.

Each of the upper grooves TG1 and TG2 overlaps with the lower layers605[1] to 605[k].

The second upper groove TG2 extends in the third direction III andpenetrates the second upper layers 605[m+1] to 605[n] and the firstupper layers 605[k+1] to 605[m] between the first upper groove TG1 andthe grooves G31 to G35. The second upper groove TG2 may overlap with thelower stack structure LST and an uppermost lower layer 605[k] may be abottom surface of the second upper groove TG2.

The first upper groove TG1 extends in the third direction III andpenetrates the second upper layers 605[m+1] to 605[n]. The first uppergroove TG1 overlaps with the first upper layers 605[k+1] to 605[m]. Thatis, an uppermost first upper layer 605[m] may be a bottom surface of thefirst upper groove TG1.

Each of the lower layers 605[1] to 605[k], the first upper layers605[k+1] to 605[m], and the second upper layers 605[m+1] to 605[n],which constitute the gate stack structure ST21, may include firstconnection parts LP11 and a second connection part LP12.

Each of the upper grooves TG1 and TG2 and the grooves G31 to G35 may befilled with a gap fill insulating layer 641. Each of the upper groovesTG1 and TG2 and the grooves G31 to G35 may stepped sidewalls. Thestepped sidewalls may have steps formed by the thin films 605[1] to605[n] constituting the gate stack structure ST21, and provide padregions connected to contact plugs 671. Each of the contact plugs 671may extend in the third direction III to penetrate the gap fillinsulating layer 641.

Each of the second upper groove TG2 and the grooves G31 to G35 mayinclude a first stepped structure and a second stepped structure, whichhave different gradients and face each other. The first steppedstructure and the second stepped structure may be the same structuresdescribed with reference to FIG. 4A.

The first upper groove TG1 may include third stepped structures thatface each other and are symmetrical to each other. The third steppedstructure may be the same as the structure described with reference toFIG. 4B.

Conductive layers constituting the thin films 605[1] to 605[k] includedin the gate stack structure ST21 may include word lines connected tomemory cells and select lines connected to select transistors. Forexample, conductive layers included in the second upper layers 605[m+1]to 605[n] of the gate stack structure ST21 may be used as first selectlines, and conductive layers included in the first upper layers 605[k+1]to 605[m] and the lower layers 605[1] to 605[k] of the gate stackstructure ST21 may be used as word lines or second select lines.

FIGS. 27A and 27B are perspective views illustrating structures whichare shown in FIG. 25. FIGS. 27A and 27B illustrate a portion of the gatestack structure.

Referring to FIGS. 27A and 27B, the upper grooves TG1 and TG2 aredisposed in the upper stack structure UST, and overlap with the lowerstack structure LST. The grooves G31 to G34 penetrate all layers of theupper stack structure UST, and have different depths in the lower stackstructure LST.

The first upper groove TG1 is surrounded by the second upper layers605[m+1] to 605[n]. The first upper groove TG1 has sidewalls that faceeach other and are symmetrical to each other. Sidewalls of the firstupper groove TG1 may have the third stepped structure SW3 described withreference to FIG. 4B. The first upper groove TG1 overlaps with the firstupper layers 605[k+1] to 605[m].

The second upper groove TG2 is surrounded by the second upper layers605[m+1] to 605[n] and the first upper layers 605[k+1] to 605[m]. Thesecond upper groove TG2 overlaps with the lower stack structure LST. Thesecond upper groove TG2 may have asymmetrical sidewalls that face eachother and have different gradients. One of the sidewalls of the secondupper groove TG2 may have the first stepped structure SW1 shown in FIG.4A, and the other sidewall of the second upper groove TG2 may have thesecond stepped structure SW2 shown in FIG. 4A.

Each of the grooves G31 to G34 may have a sidewall with the firststepped structure SW1 shown in FIG. 4A and a sidewall with the secondstepped structure SW2 shown in FIG. 4A. For example, the first grooveG31 may include first to third sidewalls S1 to S3 described withreference to FIG. 5A, and a second groove G32 may include forth to sixthsidewalls S4 to S6 described with reference to FIG. 5A.

The first upper layers 605[k+1] to 605[m] and the second upper layers605[m+1] to 605[n] may surround each of the grooves G31 to G34.

FIGS. 28A and 28B, 29A and 29B, and 30A to 30D are views illustrating amethod of manufacturing a semiconductor memory device in accordance withan embodiment of the present disclosure. The gate stack structuresdescribed with reference to FIGS. 25, 26A, 26B, 27A, and 27B may beformed as described below.

FIGS. 28A and 28B are plan and sectional views illustrating an etch stoppattern 711 on a stack structure 700. FIG. 28B illustrates across-section of the stack structure 700 taken along line Cb-Cb′ shownin FIG. 28A.

Referring to FIGS. 28A and 28B, the stack structure 700 is formed bystacking a plurality of horizontal layers 705[1] to 705[n] on a lowerstructure 701. The lower structure 701 may be the same as the lowerstructure 101 described with reference to FIGS. 2A and 2B. After aninsulating layer 703 covering the lower structure 701 is formed, thestack structure 700 may be formed on the insulating layer 703.

Each of the horizontal layers 705[1] to 705[n] of the stack structure700 may include a cell region R1 and a contact region R2 extending in ahorizontal direction from the cell region R1. The horizontal layers705[1] to 705[n] may include lower layers 705[1] to 705[k], first upperlayers 705[k+1] to 705[m], and second upper layers 705[m+1] to 705[n].

Each of the horizontal layers 705[1] to 705[n] may be formed byalternately stacking first material layers and second material layers asdescribed with reference to FIGS. 7A and 7B.

Subsequently, an etch stop pattern 711 may be formed on the stackstructure 700. Before the etch stop pattern 711 is formed, the channelstructures CH shown in FIG. 25 may be formed in the cell region R1 ofthe stack structure 700.

The etch stop pattern 711 may be formed of a material different fromthose of the stack structure 700 and mask patterns formed in asubsequent process. For example, the etch stop pattern 711 may be a hardmask material as described above with respect to etch stop pattern 513.

The etch stop pattern 711 may extend to the contact region R2 from thecell region R1. The etch stop pattern 711 may include a first openingOP21 and second openings OP22, which locally open the stack structure700 in the contact region R2.

The first opening OP21 may be disposed between the cell region R1 andthe second openings OP22. Accordingly, the first opening OP21 may beformed closer to the cell region R1 than the second openings OP22. Awidth WC of the first opening OP21 may be narrower than a width WD ofeach of the second openings OP22.

FIGS. 29A and 29B are views illustrating a process of forming a firstupper groove TG1 and first preliminary grooves PGa. FIG. 29A is a planview illustrating a first mask pattern 713. FIG. 29B illustrates across-section of the stack structure 700 taken along line Cb-Cb′ shownin FIG. 29A.

Referring to FIGS. 29A and 29B, the first mask pattern 713 may be formedon the etch stop pattern 711 to cover the stack structure 700. The firstmask pattern 713 may include a photoresist pattern. The first maskpattern 713 may have a third opening OP23 that exposes the first openingOP21 and fourth openings OP24 that respectively expose the secondopenings OP22.

Each of the second upper layers 705[m+1] to 705[n] is etched using thefirst mask pattern 713 and the etch stop pattern 711 as an etch mask, sothat the first upper groove TG1 and the first preliminary grooves PGaare formed. The first upper groove TG1 may be defined by etchingportions of the second upper layers 705[m+1] to 705[n] which are exposedby the first opening OP21 and the third opening OP23. The firstpreliminary grooves PGa may be defined by etching portions of the secondupper layers 705[m+1] to 705[n] which are exposed by the second openingsOP22 and the fourth openings OP24.

Each of the first upper groove TG1 and the first preliminary grooves PGamay include opposing sidewalls. Both of the opposing sidewalls may havestepped structures that are symmetrical to each other. Each of thestepped structures may have the third stepped structure SW3 describedwith reference to FIGS. 4A to 4B.

The stepped structures of each of the first upper groove TG1 and thefirst preliminary grooves PGa may be formed by repeating an etchingprocess and a slimming process as described with reference to FIGS. 7Aand 7B.

FIGS. 30A to 30D are plan views illustrating processes of etching aportion of each of the first preliminary grooves PGa shown in FIGS. 29Aand 29B.

Referring to FIG. 30A, the stack structure 700 shown in FIG. 29B may beetched using a second mask pattern 715 covering a portion of each of thefirst preliminary grooves PGa. Before the second mask pattern 715 isformed, the first mask pattern 713 shown in FIGS. 29A and 29B may beremoved. The second mask pattern 715 may include a photoresist pattern.

The second mask pattern 715 may extend to completely cover the firstupper groove TG1 and the cell region R1. The second mask pattern 715 mayinclude fifth openings OP25. The fifth openings OP25 may overlap withthe second openings OP22, respectively. The fifth openings OP25 may bebiased toward one side of the first preliminary grooves PGa.

Each of the first upper layers 705[k+1] to 705[m] shown in FIG. 29B maybe etched using the etch stop pattern 711 and the second mask pattern715 as an etch mask. Accordingly, the second upper groove TG2 shown inFIGS. 25, 26A, and 27A is formed. During the etching process for formingthe second upper groove TG2, the second stepped structure SW2 describedwith reference to FIG. 4A may be formed using openings OP25 and thesecond openings OP22. The second stepped structure SW2 may be formed byrepeating the etching and slimming processes which are described withreference to FIG. 8C.

Through the process described with reference to FIG. 30A, one of thefirst preliminary grooves PGa may be changed to have the shape of thesecond upper groove TG2 at a position shown in FIG. 30B, and theremaining first preliminary grooves PGa may be changed to the shape ofsecond preliminary grooves PGb, which is the same as the second uppergroove TG2, at positions shown in FIG. 30B.

Referring to FIG. 30B, after the second upper groove TG2 and the secondpreliminary grooves PGb are formed, the second mask pattern 715 shown inFIG. 30A may be removed. Subsequently, a third mask pattern 717 may beformed, which has sixth openings OP26 opening some of the secondpreliminary grooves PGb, and completely covers the remaining secondpreliminary grooves PGb. The third mask pattern 717 may be formed on theetch stop pattern 711. The third mask pattern 717 may include aphotoresist pattern.

The third mask pattern 717 may extend to completely cover the firstupper groove TG1, the second upper groove TG2, and the cell region R1.The sixth openings OP26 may overlap with some of the second openingsOP22, respectively.

In order to form the first groove G31 shown in FIGS. 25, 26A, and 27A,at least some of the lower layers 705[1] to 705[k] shown in FIG. 29B maybe etched using the etch stop pattern 711 and the third mask pattern 711as an etch mask. A structure with the same structure as the stackstructure 300 shown in FIG. 9B may be formed by the etching process forforming the first groove G31.

The etched second preliminary grooves PGb may be a first groove G31 andthird preliminary grooves PGc as shown in FIG. 30C.

Referring to FIG. 30C, after the first groove G31 and the thirdpreliminary grooves PGc are formed, the third mask pattern 717 shown inFIG. 30B may be removed. Subsequently, a fourth mask pattern 719 may beformed, which has seventh openings OP27 that expose the thirdpreliminary grooves PGc and the remaining second preliminary grooves PGband completely covers the upper grooves TG1 and TG2 and the first grooveG31. The fourth mask pattern 719 may be formed on the etch stop pattern711. The fourth mask pattern 719 may include a photoresist pattern.

The fourth mask pattern 719 may extend to completely cover the cellregion R1. The seventh openings OP27 may overlap with some of the secondopenings OP22.

In order to form the second groove G32 and a third groove G33, which areshown in FIGS. 25, 26A, and 27A, at least some of the lower layers705[1] to 705[k] shown in FIG. 29B may be etched using the etch stoppattern 711 and the fourth mask pattern 719 as an etch mask. A sectionalstructure with the same shape as the stack structure 300 shown in FIG.10B may be formed by etching the second groove G32 and the third grooveG33.

The grooves exposed by the seventh openings OP27 may be a second grooveG32 and a fourth preliminary groove PGd as shown in FIG. 30D. Thegrooves exposed by the seventh openings OP27 may be a third groove G33and a fifth preliminary groove PGe as shown in FIG. 30D.

Referring to FIG. 30D, after the second and third grooves G32 and G33and the fourth and fifth preliminary grooves PGd and PGe are formed, thefourth mask pattern 719 shown in FIG. 30C may be removed. Subsequently,a fifth mask pattern 721 may be formed, which has eighth openings OP28that expose the fourth and fifth preliminary grooves PGd and PGe andcompletely covers the upper grooves TG1 and TG2 and the first to thirdgrooves G31 to G33. The fifth mask pattern 721 may be formed on the etchstop pattern 711. The fifth mask pattern 721 may include a photoresistpattern.

The fifth mask pattern 721 may extend to completely cover the cellregion R1. The eighth openings OP28 may overlap with some of the secondopenings OP22, respectively.

In order to form the fourth groove 34 and the fifth groove 35, which areshown in FIGS. 25, 26A, and 27A, at least some of the lower layers705[1] to 705[k] shown in FIG. 29B may be etched using the etch stoppattern 711 and the fifth mask pattern 721 as an etch mask. A sectionalstructure with the same shape as the stack structure 300 shown in FIG.11B may be formed by the etching process for forming the fourth grooveG34 and the fifth groove G35.

Subsequently, the fifth mask pattern 721 may be removed, and a processof forming a gap fill insulating layer as described with reference toFIGS. 22A and 22B, a first planarization process as described withreference to FIG. 23, and a second planarization process and a processof forming a slit as described with reference to FIGS. 24A and 24B maybe sequentially performed.

FIG. 31 is a block diagram illustrating a configuration of a memorysystem in accordance with an embodiment of the present disclosure.

Referring to FIG. 31, the memory system 1100 in accordance with theembodiment of the present disclosure includes a memory device 1120 and amemory controller 1110.

The memory device 1120 may be a multi-chip package configured with aplurality of flash memory chips. The memory device 1120 may include anyone of the semiconductor memory devices described with reference toFIGS. 1A, 1B, 2A, 2B, 3, 4A and 4B, 5A and 5B, 6, 13A and 13B, 14A and14B, 15, 16, 25, 26A and 26B, and 27A and 27B.

The memory controller 1110 is configured to control the memory device1120, and may include a static random access memory (SRAM) 1111, a CPU1112, a host interface 1113, an error correction code (ECC) 1114, and amemory interface 1115. The SRAM 1111 is used as an operational memory ofthe CPU 1112, the CPU 1112 performs overall control operations for dataexchange of the memory controller 1110, and the host interface 1113includes a data exchange protocol for a host connected with the memorysystem 1100. The ECC 1114 detects and corrects errors in data read fromthe memory device 1120, and the memory interface 1115 interfaces withthe memory device 1120. In addition, the memory controller 1110 mayfurther include a ROM for storing code data for interfacing with thehost, and the like.

The memory system 1100 configured as described above may be a memorycard or a Solid State Drive (SSD), in which the memory device 1120 iscombined with the controller 1110. For example, when the memory system1100 is an SSD, the memory controller 1100 may communicate with anexternal entity (e.g., the host) through various interface protocols,such as a Universal Serial Bus (USB) protocol, a Multi-Media Card (MMC)protocol, a Peripheral Component Interconnection (PCI) protocol, aPCI-Express (PCI-E) protocol, an Advanced Technology Attachment (ATA)protocol, a Serial-ATA (SATA) protocol, a Parallel-ATA (PATA) protocol,a Small Computer Small Interface (SCSI) protocol, an Enhanced Small DiskInterface (ESDI) protocol, and an Integrated Drive Electronics (IDE)protocol.

FIG. 32 is a block diagram illustrating a configuration of a computingsystem in accordance with an embodiment of the present disclosure.

Referring to FIG. 32, a computing system 1200 in accordance with theembodiment of the present disclosure may include a CPU 1220, a randomaccess memory (RAM) 1230, a user interface 1240, a modem 1250, and amemory system 1210, which are electrically connected to a system bus1260. When the computing system 1200 is a mobile device, a battery forsupplying an operation voltage to the computing system 1200 may befurther included, and an application chip set, a Camera Image Processor(CIS), a mobile D-RAM, and the like may be further included.

In an embodiment of the present disclosure, grooves disposed atdifferent depths in a contact region of a stack structure are providedwith sidewalls having a stepped structure, so that the stepped structurecan be used as a pad region connected to a contact plug.

In an embodiment of the present disclosure, the grooves are locallyformed in thin films making up the stack structure. Accordingly, thethin films extend to both sides of a contact region of the stackstructure, so that both sides of the contact region can be used as acell region.

In an embodiment of the present disclosure, each of the thin filmsconstituting the stack structure remains in the contact region, so thatthe stability of a manufacturing process can be ensured. Accordingly,the structural stability of the three-dimensional semiconductor memorydevice can be improved.

In an embodiment of the present disclosure, some of sidewalls definingeach of the grooves have a stepped structure, and the other sidewallshave a gradient greater than that of the stepped structure. Accordingly,the area occupied by the grooves is decreased, and thus the degree ofintegration of the semiconductor memory device can be improved.

In an embodiment of the present disclosure, an etching process of thestack structure can be performed such that regions of the stackstructure, which are individually exposed by mask patterns used as anetch mask, overlap with each other. Accordingly, the grooves disposed atdifferent depths can be easily formed.

In embodiments of the present disclosure, forming a semiconductor deviceincludes applying and removing photoresist layers several times to forma series of grooves. When a hard mask layer is present in conjunctionwith the photoresist layers, the thickness photoresist layers can besubstantially reduced, and the amount of time to create and remove thephotoresist layers is substantially reduced, leading to higherthroughput and lower defects and cost. In addition, because openings inthe hard mask pattern are used to form the grooves, tolerances of thephotoresist mask can be much greater.

Embodiments of the present disclosure have been described in thedrawings and specification. Specific terminologies have been used toexplain specific embodiments of the present disclosure. However, thepresent disclosure is not restricted to the above-described embodiments,and many variations are possible within the scope of the presentdisclosure. It should be apparent to those skilled in the art thatvarious modifications can be made based on the technological scope ofthe present disclosure in addition to the embodiments disclosed herein.

What is claimed is:
 1. A semiconductor memory device comprising: a lowerstack structure having a cell region and a contact region extending in ahorizontal direction from the cell region, wherein the lower stackstructure includes lower layers stacked on each other, and the lowerlayers include first patterns and second patterns disposed on the firstpatterns; a first groove surrounded by the second patterns in thecontact region, the first groove overlapping with the first patterns;and a second groove surrounded by the first patterns and the secondpatterns in the contact region, wherein the first groove has a firstsidewall defined along sidewalls of the second patterns and a secondsidewall and a third sidewall, which extend from the first sidewall andface each other, and the second groove has a fourth sidewall definedalong sidewalls of the first patterns and a fifth sidewall and a sixthsidewall, which extend from the fourth sidewall and face each other,wherein each of the second sidewall and the fifth sidewall has a firststepped structure, and each of the third sidewall and the sixth sidewallhas a second stepped structure.
 2. The semiconductor memory device ofclaim 1, wherein the first stepped structure and the second steppedstructure have different gradients.
 3. The semiconductor memory deviceof claim 1, wherein each of the first sidewall and the fourth sidewallhas a gradient greater than those of the first stepped structure and thesecond stepped structure.
 4. The semiconductor memory device of claim 1,wherein the second groove includes seventh to ninth sidewalls, whereinthe seventh to ninth sidewalls are defined along the sidewalls of thesecond patterns, and are respectively connected to the fourth to sixthsidewalls.
 5. The semiconductor memory device of claim 1, furthercomprising an upper stack structure including first upper layers stackedon the lower stack structure and second upper layers stacked on thefirst upper layers.
 6. The semiconductor memory device of claim 5,further comprising: a first trench penetrating the second upper layersbetween the cell region and the first groove, the first trenchoverlapping with the first upper layers; a second trench penetrating thesecond upper layers and the first upper layers between the first trenchand the first groove, the second trench overlapping with the lower stackstructure; and third trenches penetrating the second upper layers andthe first upper layers to respectively open the first and secondgrooves.
 7. The semiconductor memory device of claim 6, wherein theupper stack structure is separated into a cell structure overlappingwith the cell region and a dummy structure overlapping with the contactregion by the first trench, the second trench, and the third trenches.8. The semiconductor memory device of claim 6, wherein the first trenchhas sidewalls that face each other to be symmetrical to each other, andeach of the second and third trenches has sidewalls that face each otherand have different gradients.
 9. The semiconductor memory device ofclaim 6, wherein one of both sidewalls of each of the second and thirdtrenches has the first stepped structure, and the other of both thesidewalls of each of the second and third trenches has the secondstepped structure.
 10. The semiconductor memory device of claim 6,wherein end portions of the second upper layers, which extend toward asidewall of the first trench from the cell region, form a third steppedstructure, wherein an upper portion of the first stepped structure hasthe third stepped structure.
 11. The semiconductor memory device ofclaim 5, further comprising: a first upper groove surrounded by thesecond upper layers between the cell region and the first groove, thefirst upper groove having sidewalls that face each other and aresymmetrical to each other, the first upper groove overlapping with thefirst upper layers; and a second upper groove surrounded by the secondupper layers and the first upper layers between the first upper grooveand the first groove, the second upper groove having sidewalls facingeach other, the second upper groove overlapping with the lower stackstructure, wherein the first upper layers and the second upper layersextend to the contact region from the cell region to surround each ofthe first and second grooves.
 12. The semiconductor memory device ofclaim 11, wherein the sidewalls of the second upper groove havedifferent gradients.
 13. The semiconductor memory device of claim 11,wherein one of the sidewalls of the second upper groove has the firststepped structure, and the other of the sidewalls of the second uppergroove has the second stepped structure.
 14. The semiconductor memorydevice of claim 5, wherein each of the lower layers, the first upperlayers, and the second upper layers is formed in a stacking structure ofan interlayer insulating layer and a conductive layer.
 15. Thesemiconductor memory device of claim 5, further comprising channelstructures penetrating the upper stack structure and the lower stackstructure in the cell region.
 16. The semiconductor memory device ofclaim 1, wherein the first stepped structure and the second steppedstructure are symmetrical to each other.
 17. The semiconductor memorydevice of claim 1, further comprising: an upper stack structureincluding upper layers stacked on the lower stack structure; a firsttrench penetrating the upper layers between the cell region and thefirst groove, the first trench overlapping with the lower stackstructure; and second trenches penetrating the upper layers torespectively open the first and second grooves.
 18. The semiconductormemory device of claim 17, wherein the upper stack structure isseparated into a cell structure and dummy structures by the first trenchand the second trenches, the cell structure overlapping with the cellregion, the dummy structures overlapping with the contact region. 19.The semiconductor memory device of claim 17, wherein each of the firstand second trenches has sidewalls that face each other to be symmetricalto each other.
 20. The semiconductor memory device of claim 17, whereinone of the sidewalls of each of the first and second trenches has thefirst stepped structure, and the other of the sidewalls of each of thefirst and second trenches has the second stepped structure.
 21. Thesemiconductor memory device of claim 17, wherein each of the lowerlayers and the upper layers is formed in a stacking structure of aninsulating layer and a conductive layer.
 22. The semiconductor memorydevice of claim 17, further comprising channel structures penetratingthe upper stack structure and the lower stack structure in the cellregion.
 23. A semiconductor memory device comprising: a stack structureincluding conductive layers stacked in a vertical direction, the stackstructure having a cell region and a contact region extending in ahorizontal direction from the cell region; and grooves formed in thestack structure in the contact region, the grooves being spaced apartfrom each other in the horizontal direction, the grooves having bottomsurfaces disposed at different heights, wherein each of the grooves issurrounded by a first stepped structure, a second stepped structure, anda sidewall defined by connection parts of the conductive layers, whereinthe first stepped structure and the second stepped structure face eachother, wherein the connection parts connect the first stepped structureand the second stepped structure.
 24. The semiconductor memory device ofclaim 23, wherein the first stepped structure and the second steppedstructure have different gradients.
 25. The semiconductor memory deviceof claim 23, wherein the sidewall has a gradient greater than those ofthe first stepped structure and the second stepped structure.
 26. Thesemiconductor memory device of claim 23, wherein the first steppedstructure and the second stepped structure are symmetrical to eachother.